I agree, and I'm not sure why it feels off but I have a theory.

AI is good at local coherence, but loses the plot over longer thoughts (paragraphs, pages). I don't think I could identify AI sentences but I'm totally confident I could identify an AI book.

This includes both opening a large text in a way of thinking that isn't reflected several paragraphs later, and also maintaining a repetitive "beat" in the rhythm of writing that is fine locally but becomes obnoxious and repetitive over longer periods. Maybe that's just regression to the mean of "voice?"