It's especially essential to mark the code as AI generated. AI makes mistakes just as humans do. Problem is AI makes different kinds of mistakes than humans.

A human will tend to forget to do something they were supposed to do. An AI will do a bunch of unnecessary shit.

Also you can tell that a human didn't put a lot of thought into some code (no comments, sloppy variable names) so you're more likely to say "yeah ok, I used to make that kind of mistake when I was younger" and just fix it. AI generated code will have all kinds of comments which normally makes you more hesitant before making a change. It looks like someone really thought through what they were doing, but in reality it's something generated by an LLM and no real thought was given to the code.