I'm not sure what you mean by chunks of images. My understanding is that it's a perceptual hash meant to determine if it's the same image, with minor adjustment

I'm not sure what you mean by chunks of images. My understanding is that it's a perceptual hash meant to determine if it's the same image, with minor adjustments like cropping or adjusting the colors. There is no AI/ML classification running. Apple says false positives occur at a rate of one in a trillion or something like that. Someone elsewhere in the thread calculated that this would not be frequent enough for false positives to trigger a manual review.