Disclaimer: this is purposefully obtuse.
Other effects in the game which explicitly state they kill you:
Shadows, succubi, massive damage, death saving throws, beholder death ray (notably not even their disintegration ray kills you), power word kill, vampires, mind flayers, night hags, drow inquisitors.
Clearly, if they intended for disintegration to kill you, they'd have said so. Since specific overrides general, and there is no general rule that disintegrated creatures are dead, I rest my case. QED.
I disagree, I think it's funny as long as this is all theory.
If a player was actually serious about wanting to do this as more than a meme, and was arguing this hard for it I'd be mad as hell. In this context, though? It's fine. I think it's amusing how hard people can stretch the rules. It's similar to the peasant railgun. Hilarious concept. I'm still not okay with someone trying to actually use a peasant railgun.
In theory, sure. But not with OP saying "Nah-uh" to everything. There's just no fun to be had.
And I really enjoy arguing about game mechanics, just look back at me talking about that insect swarm/animal shapes nonsense people who know nothing about the game came up with.
I'd say I'd agree but there is no stretching here, you'd have to rule that a creature that is missing every part of its body is alive. You'd also have to rule that a pile of dust has a maximum HP of more than 0, or else you'd also be dead instantly.
You'd never get a death save, your already dead.