> You could probably detect essay cheating (AI written) in the exact same way by questioning the student about it - why did they organize the essay in this way, what was their motivation for focusing on X, or expressing something as Y... Of course anyone can concoct an explanation on the fly, but it should be obvious if they are speaking from the experience of having authored it or just coming up with a post-hoc rationalization.

I wouldn't claim that I am bad at writing (at least in my native language, which is not English) - at least many colleagues say so. But I do insist that when writing I don't think that way. If I were to answer these question, my honest answers would be:

"why did they organize the essay in this way": I just wrote down the thoughts that came to my mind, and then gave them some structure that seemed right.

"what was their motivation for focusing on X": Either "because it felt right" or "I had to write at most x pages, and indeed it would have made sense to focus on more topics, so I focused on this arbitrary thing"

So indeed I would claim that a lot of sensible reasons why things are this way actually are post-hoc rationalizations. :-)