I dropped an image that was color corrected with AI, but otherwise a proper image of myself. I use my own face because it's very easy to see if AI has altered it in a subtle way when dealing with a very familiar subject.

It found the "AI Generated" signature embedded in it by the creator (whatever image model Perplexity decided to use.)

But I wouldn't have called this image AI. So images that have merely been color corrected or other very minor changes may come up as "AI Generated" even if they're essentially real images.