I still also totally don't get their policy.
Trying to avoid false positives by not firing until a threshold was hit (was it 20 images?) seemed insane from a PR position... rightly or wrongly, all it would take would be the wrong court case and you can see the headlines:
"Apple says users can have up to 20 CSAM images on their phone before they'll tell police"
The practical problem is, without a threshold, they'd have an order of magnitude more false positives than 'real' detections, making the system useless.
Imagine you have pictures of someones baptism and the kid was nude. Is it CSAM? I think the program would have to say use but morally I'd say no. The issue with client scanning is it has to assume the worst, or they are than liable. If its the person has 20+ different baptism of nude babys well huh that actually might be CSAM because the context of how that concentrated photos implies but even than its hard what if that person actually has 20 God Children its less crazy than one thinks... Especially if they have multiply phones from a single baptism.
You might not like pictures that way but honestly I think more important in procescuting CSAM is to go after the large sources of CSAM generation. Its trafficing in East Asia, and in Europe. I think weirdly America actually produces less CSAM in general because Americans are lot more off put by Sex than most other cultures. Abuse definitely happens in the US but making policy decisions like this produces bad policy.
Does iCloud rehost the photos to other people I don't really know because I use andriod tbh. If they are being rehosted (I assume to members of your contacts) that can be problematic but I think honestly the issue a lot more complex than just protect the children which the source of critic is a lot attacks against apples are coming from