Apple has always made clear that information stored on their iCloud service were subject accesses by a third party with the proper authority. Whether this third party is US or Chinese does not change anything.
Only the information that is resident on your phone with the Secure Enclave is tamper resistant.
Again, it's not so much about what the firm can actually do with the infrastructure (ideally, it's a black box that only the user can access with the correct key), but what compromise they're willing to make in order to conduct business. Privacy has become a selling point for Apple, and actions like these signal how serious they are about it.