Well, for reasons, I happen to know that this person is a student, who has effectively no experience dealing with real-world codebases.

It's possible that the LLM produced good results for the small codebases and well-known exercises that they had to deal with so far.

I'm also guessing, they're learning what a PR is for the first time just now. And then being taught by Microsoft that you can just fire off PRs without a care in the world, like, yeah, how should they know any better?