> LLMs often use em-dashes without spaces before and after, as a period replacement. Now that is only what an Oxford professor would write probably, I've never seen a human write text like that. So those specific em-dashes is a sure sign of a generated slop.

Evidently, you've never read text from anyone whose job requires writing, publishing, and/or otherwise communicating under rules established in (e.g.) the Chicago Manual of Style.