1) Well, MotoGP bikes have been using these for a few years now. As I understand it, the purpose there is to help them retain heat, because the fancy carbon brakes don't work nearly as well when not hot.
2) In other applications, brake covers also help keep debris off the calipers and pads and, contrary to the above, help keep things cool.
I did a search for disc brake covers at Revzilla.com, and then clicked on the first item. That product's description:
View attachment 4152
3) However, in the case of the CE-04, my
guess is that it's for aerodynamic purposes. That is, there's a lot of turbulence, "dirty" air, around unstreamlined areas on a bike, and I suspect that the engineers are trying to do what they can to ameliorate that, given the already-limited range of that bike. From my general-purpose reading, manufactures of EV cars are more concerned with aerodynamic efficiencies than they are with ICE cars, too.
That's my guess, anyway.