Maxperson
Morkus from Orkus
As to that, whenever we come across RAW that could be read in either of two ways, and the wording doesn't solve the problem, then go to the concept behind the effects in question.
With disintegrate, what the 'dust at 0hp' rule is trying to simulate is that if you would otherwise die or be knocked unconscious from the damage dealt by this spell, it turns you to dust.
But the beast form going to 0hp does not result in the usual death/unconsciousness; it results in a reverted druid, who takes the excess damage.
RAW cannot be read both ways. RAW is read able to be read one way. Damage reducing you to 0 hit points = dust. Druid wild shape hits 0 hit points. It's crystal clear.
There is no dead/unconscious beast, therefore there is no dust.
You are confusing intent with RAW. RAI =/= RAW.