Things can be visually identical but not the same. What you're saying is that someone might take a photo that is visually identical to some of the worst know sexual abuse imagery of children, but it's not the same photo, it's a new one.
Is that really the argument you want to make here?
The point is that the false positive won't generally look anything like the target CSAM image. These two images have the same NeuralHash:
View attachment 2253909View attachment 2253910
So do these:
View attachment 2253911View attachment 2253912
In both cases images of dogs were used as the target database and other images were manipulated until they matched the hash-- so the false positive isn't a natural image it was modified until it matches (notice the color splotches on hte lower car image).
If you notice, a false positive doesn't mean you have another image similar to a dog and in the CSAM case it wouldn't mean you have a picture anything like a CSAM image.
So the reason to set a false positive threshold is to account for the fact that hashes are data reductive by definition and you can sometimes hit a match by accident. If that were to happen 30 times in images you were uploading to iCloud, then it would trigger a manual review- not of your images but of an encrypted derivative of the image. I'm not sure what that derivative is but presumably it's not the whole image because they don't want their reviewers to be subjected to the image from true positives.
So if it's a car rather than previously known child abuse, the manual reviewer would reject it. If it's a loving parent taking a photo of a baby in a bathtub rather than previously known child abuse, the manual reviewer would reject it. It if was previously unknown child abuse rather than previously known child abuse, the manual reviewer would reject it.
If you're unlucky enough to get flagged for an image that is visually identical to, but is not, previously known child abuse then your lawyer has their work cut out for them.