My complaint is not about guarantees, it's about defaults. Default non-e2e-encrypted backups of message encryption keys are the problem here. No system can guarantee absolute security, but that doesn't mean they're all equivalently bad. Some are definitely more secure than others, and defaults have a lot to do with it!

> Some are definitely more secure than others, and defaults have a lot to do with it!

That's great, naming those would have been better though since it would have actually answered the question.

You are attacking a straw man. The risk is the your correspondent does not have ADP enabled, as it is not on by default, and not even offered in some authoritarian countries like the U.K., so even without their cooperation they can still get their key. I don’t know if iMessage implements Perfect Forward Secrecy, but at the very least they will be able to read all your messages moving forward.