Why would they distribute the ML weights file if it isn't being used for logging or reporting? Of course I do theorize that it is actually being used.

There is so much network traffic between macOS services and the internet, I'm not sure how easy it would be for researchers to discover if CSAM reporting is enabled. Little snitch detects 292 macOS services on my M1, all talking to the internet. Network experts in Apple probably even have ways of bypassing little snitch.