They say the charge capacity is 1017 mAh/g. That is about four times the value of a typical (good!) Li-Ion battery.
A quick google suggests Na-S cells at high temperatures are ~2.1V nominal (as opposed to 3.2V for LFP), but I lack the physics chops to parse the paper in the article to validate this. Anyway this sounds like a tiny experimental cell and for real world applications you'd want to see the Wh/kg for a fully packaged product.
Oh, absolutely, there's still a lot of stuff that could prohibit this technology from ever becoming an actual product. AFAICS, they also don't say anything about dependence an ambient temperature, for instance. It might be that this thing disintegrates as soon as it's freezing. Or, actually the most likely: that it's simply not possible to build this thing at scale with reasonable cost.
Plus the voltage difference... IIRC, Na-S is 2.1V compared to 3.7V nominal for Lithium-ion, high voltage versions sometimes up to 4.35V max voltage. Perhaps a factor of 2 difference in voltage, plus it's only counting a portion of the cell mass.
I think the 100 kW·h Tesla batteries found in the Model S/X weigh around 750 kg; so I guess electric air travel is still difficult unless a battery breakthrough happens; at least in terms of weight.