I tried MX Bikes' go at VR support a long time ago but I really thought it added to the experience. It was really cool to look around in the air on jumps and look ahead in turns.
I don't really play MX Bikes though, but if I did I'm sure I'd play it in VR. I'd definitely play MXS in VR if I had the option since I prefer the feel of MXS more.
As for the nausea stuff. I can be prone to getting nauseous in car rides or on planes etc, but in VR I've never felt any effects of motion sickness. I've played basically every VR game there is too, even random apps like google maps that let you fly around with zero frame of reference and it was fine.
Those guidelines are just to encapsulate everyone I think, and it seems a lot of people can actually handle it. I remember when everyone said movement in VR wasn't going to be possible because motion sickness was just unavoidable to most, so every game at some point had teleportation locomotion. Now you see basically all games offer all forms of locomotion as an option, and smooth locomotion on by default.
I vote for taking a shot at it, and see how it goes. If it were as easy as flipping a switch to ON for VR support, I'd say 100% it works. But I don't know what you'd need to actually do to get your own game running it. So there's that