Hmm. Losses from HVDC transmission are on the order of 3% per 1000km, so I'm not sure how much of a big deal it'd be for that kind of use case. Your example would only save ~6% transmission losses. An improvement yes but not really a big deal, unless the cables were far cheaper to make than current HVDC cables (which I'm doubtful about).
I think there are other use cases within devices themselves that are far more interesting for energy storage.
Superconductors have a critical field, you can't pump unlimited amounts of current through a superconductor.
(I think there were some comments going around that this material has quite a low critical field, so there would have to be some substantial improvements on this even if it is superconducting)
I remember going down the rabbit hole on superconductors a few years ago and finding out that they were limited by a critical field. It was both reassuring and disappointing and largely for the same reason - there's no truly "free lunch" in nature.
Whether it's worth doing also depends on how much energy it would take to make thousands of miles of superconducting cable of similar capacity and how long such a cable would last.
I think there are other use cases within devices themselves that are far more interesting for energy storage.