I'm at a standing desk on a balance board and I had to get off. I got disorientated and nauseous just watching that. I can't even imagine spherical geometry with VR.
Well, if we see an object with our eye, we know that it is on a particular line. When the brain sees the object with two eyes, it knows that the object is where the two lines cross.
As long as they cross in front of the eyes. If they cross in the back, the math works, but the brain is not trained for it.
In spherical geometry that happens -- you see things which are just behind you, but the brain has problems interpreting that.
Simulating binocular vision is not the only approach though -- you can use a perspective where the objects appear at the correct distances, some non-Euclidean VR games do this.
How much have you played? It seems you need to get used to it -- for me it caused motion sickness initially, but after getting used to it (which did not require much playing in my case), not anymore (except with experimenting with new graphical settings). I still get motion sickness in Euclidean 3D games. Changing the options could help too.
I expect that's true. I got very strong motion sickness with VR, but after dedicating a few hours to it I can do low-motion games fine.
Mostly I've managed to make myself slightly ill with my own experiments in rendering motion in hyperbolic space, so I haven't spent too long in HyperRogue.
