Remember how everyone kicked up a giant stink about apple adding "on device CSAM scanning when uploading photos to iCloud"?
They did that precisely because it would allow them to search for CSAM without giving up any privacy. As I said back when all that rage was happening, if apple don't get to implement it this way you can be damn sure that the government is going to force them to implement CSAM scanning in a much more privacy-destroying way, and well here we are.