I agree, there's patterns that aren't hard to recognize if you have some experience.

I got 2400 with 10 in a row on first attempt.

Here's the entire decision matrix:

- Is the color, mood, composition, and level of detail exactly like most Nano Banana Pro images? If yes, AI.

- Is the composition/framing utterly perfect? If yes, AI.

- Is the subject ephemeral or random, like a candid photo or something otherwise unlikely to be photographed? If yes, not AI.

- Final decision, if there's any doubt, go entirely off of how centered the subject is.

I think some of this has more to do with the data set than the methodology. You could easily come up with a bunch of examples to fool me specifically, but alas, they didn't.