They are working on updated prototypes, and they have a version that has a closed "tire".
They are using a direct method of measuring rolling resistance -- a dynamometer. And quiet can be from dampening, which could also be causing higher rolling resistance.
This sort of tire seems to me to be able to provide lower rolling resistance; and I'm glad that someone is trying to develop this. The Tweel is non-pneumatic but it is designed to flex just like a pneumatic tire so that it can be used with the same suspension as standard tires.
I think that a more rigid wheel could provide lower rolling resistance, and that if the suspension was reworked to provide a smooth ride, that the combination would be more efficient and just as comfortable a ride. And if the suspension was regenerative, like the Levant Power shocks are, then this would provide more regenerated power than it would with pneumatic tires. The end result in theory, would be a more efficient vehicle, with more regenerative power and just as good or better ride; that would not require regular air pressure checks, and would not have punctures or blowouts.
With a car with full wheel skirts, like the Edison2 VLC or the Aptera or my CarBEN EV5, not having to check air pressure and not having to worry about changing a wheel on the side of the road would be a really good thing.
So, this type of technical development is a very good thing. Someone should be doing it. I would love to try these on CarBEN EV5 with regenerative shocks; after I get a working prototype built with standard tires.
