For student assignment cheating, only really the em dashes would still be in the output. But there are specific words and turns of phrases, specific constructions (e.g., 'it's not just x, but y'), and commonly used word choices. Really it's just a prim and proper corporate press release style voice -- this is not a usual university student's writing voice. I'm actually quite sure that you'd be able to easily pick out a first pass AI generated student assignment with em dashes removed from a set of legitimate assignments, especially if you are a native English speaker. You may not be able to systematically explain it, but your native speaker intuition can do it surprisingly well.
What AI detectors have largely done is try to formalize that intuition. They do work pretty well on simple adversaries (so basically, the most lazy student), but a more sophisticated user will do first, second, third passes to change the voice.
What AI detectors have largely done is try to formalize that intuition. They do work pretty well on simple adversaries (so basically, the most lazy student), but a more sophisticated user will do first, second, third passes to change the voice.