[modeless]

Yes, if your definition of "end-to-end encryption" means Apple can't read your messages (and I would argue that this is entirely reasonable), then the vast majority of messages sent through iMessage do not qualify. I would go so far as to say that it is false advertising to claim "iMessage is end-to-end encrypted" while Apple retains the ability to decrypt the vast majority of messages.

For what it's worth, Google's equivalent backup features do not have this loophole. Google cannot decrypt messages from your device backup without your device passcode, and while your device passcode is not a strong passphrase it is protected from brute force attacks by a hardware security module in the datacenter. I believe this is the same way Apple does it but only if you enable Advanced Data Protection.