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.
A disintegrated creature and everything it is wearing and carrying, except magic items, are reduced to a pile of fine gray dust. The creature can be restored to life only by means of a true resurrection or a wish spell.
Why would you need to be "restored to life" if you weren't dead?
Because you could later die. So a creature that has been disintegrated, and then later dies, can only be brought back by those means.
You're misreading the language. It is present-tense, not future.
I'm sorry, I don't know enough about the English language to recognise the difference. What would the phrase be in future tense?
No. He's trolling you. No Reasonable person thinks this.
If the creature dies it can be restored to life only by means of...