You could enable scanning of all files using a few bit-flips, but that doesn't have any effect - the results need to be evaluated by someone. Afaik, the system is designed such that the client side does not know whether a match occurred. So to actually report anyone based on the results of the proposed CSAM scanner, Apple also needs to upload all of the scanned files, including the client-side scan result, to figure out whether there's a match.
