Yes, you can depict a NPC of a particular race without the default racial traits. But under the core rules, if you wanted a NPC to reflect racial traits, you either applied the PHB traits (Monster Manual) or the traits in the NPC Features table (DMG).
"If you wanted" is the key phrase though, isn't it? That is what tells us that, well, if you want them to use it, then you can reference those stats. But, since it requires a desire to apply, then it is not the default state of those NPCs.
Yes, if you want to apply racial features, you can, but it is optional.
So the fact that the dwarf and gnome NPC Features have a small difference from the PHB version - one that's still broadly consistent with the PHB, we're talking exactly the same second ASI but a difference of +1 - indicates to you that they didn't think, in the core rules, that ASIs were reflective of the character race by default? Then explain why the other PHB races are consistent with the PHB. And explain why the Monster Manual, before that, just said to refer to the PHB traits. Heck, explain why they even pointed you to sources for racial traits, if you were expected to make up whatever you wanted, or use the NPC statblock as is?
The most I can see it meaning is that they did think dwarves and gnomes should get +2 to both stats, but decided to reduce the bonus to +2/+1 for gnomes and hill dwarves in the PHB, presumably to balance them with the other PC races. (Though they thought mountain dwarves should be an exception, for some reason.) That still isn't evidence that they thought there was zero correspondence between PCs and NPCs as far as ASIs, like they claim now; only that when push came to shove, game balance outranked "accuracy". (Something like that logic could have been behind the Volo's changes, as well, though I already granted that they could have been rethinking the idea of ASIs by then.)
EDIT: It also occurs to me that +2 for both stats for dwarves in the NPC Features might have just been a matter of convenience, since otherwise they'd have to separate out the two subraces; easier to just list +2 for both, since it's not a huge difference. Doesn't explain gnomes, admittedly.
I never said "zero correspondence"
But, let's start with the back end. If Volo's was when they "changed their mind" because nothing in the Volo's matches the DMG. Then that was back in 2016. So, five years ago. So, no matter what we want to say about anything else, do we agree that 5 years ago represents a change in the game?
And, no I'm not saying that the DMG chart alone shows that NPCs don't use the ASIs. But add in the MM showing us that we don't need to change them, the DMG no longer being accurate to pretty much anything. It really starts showing that the NPCs are treated differently.
Of course NPCs and PCs are treated differently. That's why they provided NPC statblocks. But they only provide you one way to represent racial traits for NPCs in the Monster Manual, and another that's basically the same (except for having monstrous options) in the DMG. By the core rules, you can either represent racial traits, or not. And ASIs were part of racial traits for both approaches.
Yes, but "If you want to do this, here is how" is vastly different than "Every NPC of this race
must have these traits."
That may be true by default for "elf", but not for "high elf" or "wood elf" or "drow", where they also get a recommended ASI at the subrace level. Under the core rules, of course - your campaign can be different.
Yes, I know there are for high elf, wood elf, Drow, Eladrin, Shadar-Kai and Eladrin. That wasn't the point. You seem to think being a "true race" is going to lead to obvious ASI's, but if we didn't have all of these elf subraces, then "elf" would have floating ASIs.
So, yeah, note that they rarely if ever give subraces and if a race is as versatile as Elves, then it becomes a case of either making six subraces, or having a floating ASI. And since they rarely make subraces....
That would require them to treat kreen subraces differently than they had other subraces up to this point, where subraces also had a recommended ASI. If they use "subraces exist" as an excuse to have floating ASI for the entire species, it would be inconsistent with how they treated every character race prior to this point. But sure, they can certainly do that; I just think it would be disingenuous.
Disingenuous really?
There are no Subraces for:
Dragonborn
Half-Elf
Half-Orc
Leonin
Satyr
Aarckrokra
Goliath
Bugbear
Goblin
Hobgoblin
Firbolg
Kenku
Kobold
Lizardfolk
Orc
Tabaxi
Triton
Yuan-Ti
Tortle
Changeling
Kalashatar
Warforged
Centaur
Loxodon
Simic Hybrid
Minotaur
Vedalken
And, in past editions, there were subraces for these types of creatures. So, would it really be disingenuous to treat them without a subrace, when the majority of races in the game don't have subraces?