The only thing about this that affects me is that you still can't put the monsters IN the adventures. I'm sorry, but I'm spoiled by the WOTC adventures, and it's VERY nice not haivng to get out my Monster Manual during combat. I don't even need much prep work. Unless publishers use their own monsters, I'll probably pass on buying any 3rd party adventures.
You hit on the core argument I made to Scott for about an hour on this point.
I said that purchasers want stat blocks in their adventures. Because if they dont have them, then they have to go to their MM, copy the stats onto a sheet, slip it in the page of the module, etc. Its harder on the DM.
If the concept is to drive purchasers to the core books, you are doing the OPPOSITE.
I am not going to fail to give the purchaser what they want. If all I can do is say "kobold skirmisher (see MM)," then I wont do that. I'd prefer to use a shortened stat block for simple monsters. So what will I do?
I will just make a cheesy substiution. Instead of a Level 1 kobold skirmisher you will fight a "level 1 kobold dragonfang" with the exact same damn stats as a kobold skirmisher except maybe HP 26 instead of 27 or something. I would make a change so small and a cosmetic name change that the monster would really be the same, but I can claim it is different enough that I am not just reprinting the monster.
Because if I do it this way, I get to put the whole damn stat block in the product! And that is what people want! So instead of incenting me to drive them to the MM you are incenting me to create a new monster that is a tiny twist on an old one just to get past that restriction, which is dumb to make me do. It means, if they are smart, NOT A SINGLE 3P module will ever include just a straight monster from the MM. Not one. And that is dumb.
What they dont want is a web site of monsters or someone doing monster cards. That, in my view, is what really drove the objection to this change. Because, taking out that issue, it doesnt make any sense to object to this.
But I blew my skill check on that and lost apparently.
Now, will there be parts of an adventure where I just list some core monsters? Sure. Maybe a random encounter table. Or in an overview of a wilderness area I might say, "In the Forest of Doom you can find werewolves, medusae and spirit devourers" or something like that. But you dont need the stat block for something like that. However, for set piece encounters, you can bet your bottom dollar I wont just say "8 ettercap fang guards" and make you go look it up. No, I will create "ettercap web guardians" that are level 4 soldiers with maybe 55 hp instead of 56 and with greatswords instead of greataxes. Then you have basically the same monster, but not I can put the whole freaking stat block in teh adventure because I just "created a new monster."