Apple’s press release is a lie.
iCloud stuff already isn’t E2E and they already scan.
This system is built exactly to surveil the entire contents of your mobile device, cloud enabled or not.
Apple has burned years of social capital in 2 days.
If the software is scanning everything, and they were already scanning uploaded content, why have a press release at all? If you're deploying an unrestricted panopticon to all your devices, why on earth would you go to the trouble of announcing it in the first place?
It looks like it only triggers when you go to upload a photo to iCloud. In that case, it (maybe?) scans only that photo on your device and then decides if it's CSAM.
I guess Apple really really doesn't want CSAM on their servers? I don't know why they wouldn't just perform the scanning on their own server otherwise.