The article seems to suggest that an attacker would be able to perform a (new) backup without unlocking the phone if they had access to a "pairing record from a

The article seems to suggest that an attacker would be able to perform a (new) backup without unlocking the phone if they had access to a "pairing record from a trusted computer", which I assume means an iTunes installation that's paired with the phone. In other words, you might have to unpair the phone (or protect the iTunes installation with FDE) in addition to deleting any backups.