The alternative they described (make it so AppleMobileBackup required a passcode only when changing the backup location) would require the phone knowing the loc

The alternative they described (make it so AppleMobileBackup required a passcode only when changing the backup location) would require the phone knowing the location of the backup and trusting the other side wasn’t lying. Might’ve been too complicated to do (especially in a way that could be applied to older versions of macOS/iTunes where AppleMobileBackup wasn’t updated).