I think the state of the art has progressed past that? A non-trivial reversal of a perceptual hash would mean that every cloud provider maintaining a CSAM scan

I think the state of the art has progressed past that? A non-trivial reversal of a perceptual hash would mean that every cloud provider maintaining a CSAM scan list violates CSAM laws - if they could reverse the hash to get too close to the original image, the hash is just a lossy storage format.