I emailed the Pydantic and FastAPI guys and didn't hear back.  Given what you found on their issue trackers, I think it's unlikely that they care a lot about this issue (but were too busy to reply).  It's far more likely that they don't care.

Doing a little research (git blame), it looks like the "follow the wrapped chain to find the original signature" work was done by Nick Coghlan about nine years ago; he touched both functools.update_wrapper and the inspect module.

The only other people to touch the code recently are Yuri and Batuhan.  I've nosied Nick and Batuhan (already looped in Yuri), just to ping them and see if they have any strong opinions.

If nobody has anything remarkable to say about it, honestly we probably *can* just merge your patch, Ofey.  I see your name is now marked with a star; are you now authorized to contribute to CPython?

(Note that I only glanced at your patch so far; if we were going to merge this bugfix I would of course first do a full review.)