This is indept. Thank you for taking the time to write this.

From your findings, I think AI currently only better at information commonly found on the internet.

Unlike fictions that conveys different styles, tones, voice, and perspectives. However, who knows? AI is evolving—it might soon improve in area of fictions in terms of understanding whether or not it's AI generated.

Also, on the other hand, your report shows that AI can't be absolutely reliable, especially for detection.