No batteries are ever anode free so you are right to call bullshit on this title ...
Yet, what they meant was that, at the time of fabrication, there is no sodium at the anode side and only while charging the battery, sodium is deposited so creating the anode.
But that's not what it's really claiming. I don't think this technology would even replace lithium ion, it would be better suited for power grid or data center storage.