I'm the owner of some of my work projects/repos. I will absolutely without a 2nd thought close a 20k LoC PR, especially an AI generated one, because the code that ends up in master is ultimately my responsibility. Unless it's something like a repo-wide linter change or whatever, there's literally never a reason to have such a massive PR. Break it down, I don't care if it ends up being 200 disparate PRs, that's actually possible to properly review compared to a single 20k line PR.