I'm getting the feeling that many people here are mostly reacting to the title instead of reading the actual policy: they state that an important part of the reason is that they use PR review to train new contributors and find possible future maintainers.

Irrespective of the quality of ai-contributions, that seems hard to argue with.

(unless you believe ai will make the whole concept of OS contributions / maintenance redundant. If that's your belief I don't think it makes much sense to submit PR's to Godot though, instead of just forking the engine and having your agents work on it)