It is easy to pick up AI copy. It has a distinctive voice that when read, sounds ... less than human. There's no personality behind the text, but not in the way that a corporate annual report is written.
It is similar the uncanny valley phenomenon in Computer Generated graphics (think high end 3D rendering) - where the lack of imperfections sets off something in our minds.
Not sure if you're read much about the uncanny valley; but it is an interesting thing to experience.
RE: AI Isn't a Threat to Human Writing