Doesn't the experiment just show that Apple is storing the iMessages in some form that they can decrypt? The article mentions iCloud backup - it's possible iClo

Doesn't the experiment just show that Apple is storing the iMessages in some form that they can decrypt? The article mentions iCloud backup - it's possible iCloud takes a copy of decrypted messages first. This might be feasible given it has to back up SMS messages too. Perhaps a better experiment would be to see if messages are readable after a restore (with and without password changes) if the device isn't backed up to iCloud.