Yes, GPT-5.2 still has adaptive reasoning - we just didn't call it out by name this time. Like 5.1 and codex-max, it should do a better job at answering quickly on easy queries and taking its time on harder queries.
Why have "light" or "low" thinking then? I've mentioned this before in other places, but there should only be "none," "standard," "extended," and maybe "heavy."
Extended and heavy are about raising the floor (~25% and ~45% or some other ratio respectively) not determining the ceiling.