I believe the motion sickness stems from your brain knowing you’re not moving but still everything you see is moving.
Happens with Lucky’s Tale for example or any game where you have to adjust the view with an additional analog stick or what have you.
The smoother and responsive everything is the less you get sick as well. Haven’t had any issues with the Vive in this aspect.
One of the main reasons why actual movement is very hard to solve at the moment.