I would think that plugging the power pack into the phone's USB port would be the more efficient route.
From an engineering perspective, I can see where a cordless charger might want a more powerful electric supply than a power pack might deliver, but that is just speculation.
They will work when plugged into a power bank but, as @ManiacJoe said, it's a lot more efficient to just plug the power bank into the phone. (Wireless chargers are notoriously inefficient.)