[OzzyB]

So in short:

Apple respected its Users' privacy and therefore only reported a low number CSAM cases since it didn't monitor and scan anything.

Facebook, because it doesn't respect its Users' privacy, wants to monitor and scan everything so it has to report large numbers of CSAM cases (in the millions).

It seems to me that the "number of CSAM cases" is a nice (perverse?) corollary to how much a particular service respects its Users privacy.