Generally speaking, hydrogen is less efficient as a store of energy than lithium-ion batteries. If you want maximum possible fuel efficiency, it has to be battery powered, not fuel cell.
Freeway fuel efficiency depends, in large part, on aerodynamics. I don’t have their specs, but just the fact that they use side-by-side seating, means that their cross section is comparable with Tesla.
If you scale that car to the point where it can go 85 mph, it will get heavier, more expensive, and less efficient. There’s no reason for it to be more economical than Tesla or Aptera.
