Idk why anyone would contribute to a project with an attitude like this

Make useful, carefully reviewed contributions and you'll be fine.

that's fine, they probably don't want you then

I don't want them either. I'll find someone else who likes me the way I am. Plenty of fish in the pond.

That seems unlikely. Probably, what is going to happen, is if during a code review, you can't actually explain what your code is doing or why you wrote it, then you will be banned.

I don't know much about this project, but looking at the diff with their previous policy, it's pretty clear that people were abusing it and not declaring that they use llms, and they don't actually know what they're doing

Then a friendlier and clearer wording for the policy would work better. The current one says you will be "immediately" banned "without recourse" which implies that nothing like you are describing will happen.