Your link doesn’t say anything like that. It talks about how Apple was planning to add e2ee encrypted backups of iMessages to iCloud but instead opted not to offer them as e2ee backups.
If you don’t enable backups for iMessages, they stay on your device.
Nowhere does it describe a back door that the FBI has access to.
> If you don’t enable backups for iMessages, they stay on your device.
The backups are enabled by default, on your device, as well as the devices of everyone else you iMessage with.
For iMessage to be end to end secured, you need to turn off iCloud Backup on each and every device you have, and everyone you iMessage with needs to turn off iCloud Backup on each and every device they have. If either you or your conversation partner misses a single device, Apple will get either the message text itself in the backup (if Messages in iCloud is disabled) or the message sync encryption key (if Messages in iCloud is enabled).
In practice, this never happens. Non-e2e iCloud Backup is an iMessage cryptographic backdoor.
Key escrow for the FBI was a cryptographic backdoor during the crypto wars in the 90s, and it is still the same today.
Defaults matter.
Apple had a plan to secure it, and (I understand) a partial implementation. It was killed specifically to aid surveillance capabilities. If that isn't a backdoor, I don't know what is.
If you don’t enable backups for iMessages, they stay on your device.
Nowhere does it describe a back door that the FBI has access to.