And you know it’s “untested and easily defeated”, how?
It's untested because it has not been used on a population as large as Apple's customer's base. The first time they engage the system, it will literally be an experiment.
It is easily defeated because algorithms have been produced already that can defeat it by subtly changing images in a way that does not impact very much on the perception of the image. There have been many threads in MR about the technical aspects of the CSAM scanning system, but you can see a preprint (so not peer-reviewed yet apparently) at this
link that shows proof of concept for evading the system. My point is that this technology sets a dangerous precedent of search without judicial review or warrant, could be used as a blueprint for invasive surveillance by authoritarian regimes, and might not even be effective. Apple should formally abandon it and move on.