The more code a PR contains, the more thorough knowledge of it the submitter must demonstrate in order to be accepted as a serious contributor.
It doesn't matter if it was written by a human or an LLM. What matters is whether we can have a productive discussion about some potential problem. If an LLM passes the test, well it's a good doggy, no need to kick it out. I'd rather talk with an intelligent LLM than a clueless human who is trying to use github as a support forum.