Some people can write 1-3k lines of good code (incl. tests) in a day when everything is just right. We used to be called 10xers lol. The 1600LOC PR is legit if trust is there, it's really a single change unit, it's not just being thrown over a wall (should have a great PR description and clear, concise commit history).
I automatically block PRs with LLM-generated summaries, commit messages, documentation, etc.