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.
If this was the intent of the rules, it would be expressed in explicit, unambiguous language. They don’t write contingency rules for possible future events that haven’t happened this way, and if you interpret rules documents this way, then everything becomes an argument.
The implication of “the creature can only be restored to life by (x)…” is present tense. It applies to the current state of the game following the events described. The language “unattended objects catch fire” in fireball doesn’t mean “unattended objects in the area of a fireball will catch fire if someone sets fire to them.” it means they catch fire.
Language in rules doesn’t ambiguously cater to a potential future state of the game that may not occur. It is describing the current state of the game, like the rules do in all other situations.
To the contrary, if it were intended to kill you it would be explicit. See all the examples I included in the OP.
The “present tense” argument doesn’t hold water when you look at how spells are worded. Let’s take a look at Alarm:
You set an alarm against intrusion…
Present tense. It describes a state change to the game world.
…Until the spell ends,…
Describes an ending to that state. We can conclude that the alarm state lasts until the spell ends.
Disintegration does not describe any such end to the changed state. We can conclude that this rider effect comes into play if the character ever dies in the future.
The “present tense” argument is that “the creature can only be restored to life” describes the current state of the creature. It’s currently possible to restore the creature to life using wish, and therefore they are currently not alive. This is a plain reading of the RAW, and it’s inconsistent with the entire cohort of the rules to claim otherwise.
If that’s not good enough for you, then it’s also the intention of “reduced to a pile of grey dust” is that players will be intelligent enough to know that dust is an object, and not a creature. There’s no statblock for the dust because objects don’t have creature stat blocks.
If THAT’S not good enough for you, it’s the intention of the rules that the players use common sense when reading them.
If THAT’S not good enough for you, Crawford has explicitly stated that if disintegrate reduces you to 0hp, you’re killed - and he wrote the rule.
Any of these four arguments should be enough for a DM to be able to make a sensible ruling here, although normally I don’t rely on an appeal-to-Crawford for rulings.
If you want to play a slapstick comedy style campaign where your DM allows things to happen outside of RAW because they’re silly or fun or whatever - there’s nothing stopping you. The joy of DnD is you can play the game however you like, so long as your group are happy with that.
Edited, because you edited your comment as I was replying: The “current state” of the creature is that it can only be brought back to life by the means mentioned in the spell, I agree with you there. But it does not mean that the creature need be dead for that to be a true statement about its state.
Would you agree with me that the normal, default state of a creature is “can only be brought back to life by [exhaustive list of all reviving magic]”?
Nothing says you become an object. Compare to True Polymorph, which has a section for turning a creature into an object.
