Guys,
What is the reason for mixing up things with A321. A321 wing has stronger structure, so no need for outer tanks.
Subject here is A320 which has outer tanks. It is no issue if the outers are empty after refuelling. No limitation mentioned. Fuel limitations concern imbalance, which is not our case. By MEL you can even dispatch with transfer valves failed (open).
Outers will become full after a while anyway if transfer valves are operating normally.