Love 'em or hate 'em, it is hard to believe Apple's lawyers haven't very carefully figured out what kind of derivative image will be useful to catch false positives but not also itself illegal CP. I assume they have in fact had detailed conversations on this exact issue with NCMEC.
Firstly, the NCMEC doesn't make the the laws. They can't therefore give any exceptional allowance to Apple.
Secondly, any derivatives that are clear enough to enable a definitive judgment whether something's CP or not by an Apple employee would be subject to my argument above. Also just collecting such material is an felony.
I don't see any way around that. Only that promising some checks before stuff gets reported for real is just a PR move to smoothen the first wave of pushback. PR promises aren't truly binding…
