Okay, I'll bite. This is my first time trying a multi quote message, so hopefully I don't screw it up.
1. Most spells can be summarized in less than a line. A couple may take 2 or may be too complex to summarize. Your CR 4 wizard will take maybe 12 lines, and your CR6 wizard might take 16. Unless you are statting out an entire wizard's guild it won't take "several pages." Even if you were statting out an entire wizard's guild, the spells will overlap and it won't take "several pages."
2. How exactly would it cut down on story content? They are two separate things. Unless you are assuming these things are written with a word count limit of some sort, in which case, where are you getting that?
3. The vitals of a spell don't really need to take more than a line. The DM doesn't need the fluff. For quick operation the DM only needs a couple of stats such as range, area, damage, and saving throw.
1. Most spells cannot be summarized in less than a line, the cantrips above would each take at least two if not 3 lines when printed out.
2. Looking at your argument later about using shorter descriptions, I can see your point here if they used shorter descriptions. 12 spells might only take 24 to 36 lines, but that is a significant portion of a column, and a wizard with that many spells might currently only take 4-6 lines for the spell names. Several spellcasters can easily add several pages in this scenario. Most of my thoughts on this are that the spell block needs to be in its entirety to be useful, and that would take up a page or two or more per wizard. Either of these scenarios would cut down on content because these books are bound in 32 page increments. So you either increase the book by 32 pages and increase the cost, or you cut pages of content to make room for the spell blocks.
3. The short description of a spell does really need to be more than a line to be useful. If all that is included is range, area, damage and saving throw, any spell that has other stuff is left out. A DM might forget that shocking grasp makes the target lose its reaction on a hit and attacks with advantage on metal armor. Or that beacon of hope can be used on any number of creatures and gives them advantage on wisdom saving throws and death saving throws and maximizes any healing they receive. Prismatic spray, as you point out later, would be a nightmare.
I'm not sure what you are arguing here. You are saying that weapons are simple but then you argued they have special abilities and are therefore not simple. Also, spell blocks DO change more than weapon blocks do. Attack spells alone have two types of attack mechanisms, up to 6 types of saving throws, and several different types of durations, actions, targeting effects and scaling mechanics, and this is without going into fluff like components. The DM can guess what a weapon does pretty handily without a lot of help, if you are unfamiliar with a particular spell you HAVE to stop play and go look it up. That is more reason why a quick-read line spell line for creatures would be helpful.
Weapons are simple and follow one of two formats: melee or ranged. The javelin shows how they both follow the same format. While they are simple, the text can be different for every NPC that uses them as the to hit and damage numbers can be different. As an aside, I mentioned that some (magic) weapons have unique abilities such as an extra die of damage or requiring a saving throw. The point was that this would be unique to that NPC (their magic item) and thus belonged with the creature. While weapons are simple, the corresponding action block is almost universally short, and each creature uses somewhere between 0 and 2 of these in there actions block. It does not take up a lot of space and includes information that can be different from one weapon to the other for the same NPC (different attack bonuses and damage bonuses for melee and ranged or magic weapons). It also fits into the 5e paradigm of writing the total modifier to a roll as one number in one place. This can be different from weapon to weapon for an NPC. So the weapon text provides a place to put those numbers.
While spells can have two types of attack mechanisms (spell attack or auto hit with DC), one of 6 different saving throws, different durations, bonus or regular or reaction actions, targets, shapes, etc. Each spell does not change. Magic Missile always has the same text. Beacon of hope always has the same text. Fireball always has the same text. Wish always has the same text. Because they take up significant space and never change, they are a prime candidate for inclusion by reference. This is what is done in the stat block for spellcasters right now. The attack roll modifier and DC are the same for a NPC across all of their spells. So these can be put in the NPC stat block instead of in the text for each spell.
That just means that the summary he proposed needs improvement. You just need to have a standardized system of notation like shorthand, and you place key of the abbreviations somewhere in the PHB. After that is easy. Most spells take less than a line. Shocking grasp has a couple of non-standard things so it wraps onto a second line. For some spells like Prismatic Spray, you may just have to say "see PHB p.XX" after special if the special effects are longer than a second line. Most of the spells which you can't easily summarize are non-combat spells though. They don't need to be summarized in a combat stat block.
Fireball: L3; CT:1A; R: 150'; AoE: 30' radius sphere; Save: Dex 1/2; Dam: 8d6 Fire; Scale: +1d6/lvl; Special: none.
Shocking Grasp: L0; CT: 1A; R: Touch-Attack; Save: No; Dam: 1d8 lightning; Scale: +1d8 5th, 11th, 17th lvl; Special: Advantage to attack if target wears metal; target hit can't take reactions until start of next turn.
The books have avoided shorthand except for the saving throws in the stat block. While you could do this, it requires the user to learn a shorthand and all writers to adhere to it. If someone changes their nomenclature or a mistake is made that passes the editors, that will throw some people off. These books and pdfs follow a two column format partially to avoid wasting space from short lines. After a 5 character indent to identify spell lines (or indicate a second line), there are about 60 characters available to the end of the line. At 116 characters, the fireball example might fit inside 2 lines, but at 217 characters, the shocking grasp example would take 4 lines. The examples above are highly compressed and already are taking up more than one line each. If page numbers were given for special effects, the DM is back to looking much of it up as many spells have a special effect. Abjuration spells are mostly special effects.
1. Again, where are you getting that a couple of extra lines increases cost to the consumer or reduces content? If they improve the players' ability to use the product I don't think WotC would object to adding a few more lines. They wasted enough text in the spell description section of the PHB that it is pretty clear they aren't that concerned about word or page counts.
2. If Hoard of the Dragon Queen is any indication, monster stat blocks come in the appendix, not in the story. There is no reason that would affect the flow of the story in any way.
3. By your reasoning there is no reason to put the monster stat blocks in any adventure either. They would also break up the story, add cost and reduce content. You can also just look them up on the monster manual just as easily as you can look the spell up.
1. Already covered books being printed in 32 page increments. If you add even a few lines per spell in a stat block, you are talking about a couple of pages once you include all of the spellcasters. At that point you have to increase the page count by 32 or drop some other content to make room. WotC is concerned about page counts. When they announced they could not fit everything they wanted in the Monster Manual, they increased it by 32 pages. They made a business decision to include certain monsters they felt were necessary while taking a hit by not raising the price of the book. pdfs would not have this problem, but if there was a pdf available, there probably would be a pdf of the necessary spells available to search.
2. You are right that it looks like the general scheme is to have the creatures at the end of the book instead of inline. I think the starter set is the same way, and the recent encounters seasons have been that way. I have had my head in a 3.5 adventure path that has the monsters and traps in-line. While the new way of doing things would not interfere with the story, placing even abridged spell blocks in the stat blocks would still require a decision to make a longer book or cut other content.
3. I absolutely agree with this. As you pointed out, the creatures are in the back of the book and not inline to the story. The only items in the appendices are the backgrounds, creatures, NPCs and magic items that are unique to the story. They are part of the unique content of the story. Every other background, magic item and creature can be found elsewhere and are not in the book. While HotDQ has an online supplement, it looks like it contains stuff that was not necessarily in basic D&D at the time, and the MM and DMG were not available at the time of HotDQ's release. Future books might not have online supplements.
If a DM wants additional spell info with a creature's stat block, they can easily copy and paste from the basic pdf or type up what they want. If they keep a list of what they typed, they only need to type each entry once and only type them as they are needed (i.e. they probably do not need to type up Wish). I do this. I do not have the spells memorized, so I have a page (or 2 or 3) of spells for the NPC so that I can quickly scan what it does and make sure I do not miss anything.