It's a good question. The only explanation that makes sense is that this now allows them to begin end-to-end encryption of iCloud photos. I see that many commen

It's a good question. The only explanation that makes sense is that this now allows them to begin end-to-end encryption of iCloud photos. I see that many commentators are claiming that they could already have started e2e encryption without introducing this "backdoor." While this is true, Apple would then be creating a perfect environment for child abusers to house their CSAM content on Apple's own servers. You can understand why Apple might not want to do that. This allows Apple to get to what is in their mind the best of both worlds: a truly private cloud for their valued users while not creating a safe haven for child abusers.