But right now all that data is available to Apple.
If they wanted to they could just generate a set of keys, replicate one of your iCloud devices, and send all your iMessages to a 3rd party, etc.
If CSAM scanning is coming, show me a better solution. I don't think there's a world ahead of us that doesn't include it for all platform-hosted photos.
My understanding from following this debacle is that law-enforcement don't have resources to investigate everyone who just have CSAM they focus on people who match and have other photos of novel abuse they can track down, and here they will only get an account name and a list of 30 CSAM photos the user had.
All this system will do is drive up Apples numbers on a "total child abuse found" scoreboard and do very little to help any actual children in need.
Still seems to be the direction the political winds are blowing.
Part of the reason for these voluntary scans is because the state would have a difficult time implementing universal spyware on its own and it needs Apple for this. This stuff is by no means certain and how "we" helps determine whether it happens. Also, the state has secretly spied and attempted to legitimatize universal spying but we've had push back on many occasions. We should keep that up.