Some people easily get motion sickness and it can be aggravated by many factors, including low and/or irregular framerates.
I’d be interested to know if people complaining about motion sickness at low fps have that issue with all games, or only FPS/TPS. And if they have the same issue with “first person” segments in movies (which are pretty damn rare in the first place, and basically always at a very consistent but low framerate)
It’s almost as if Valve thought this through when they engineered the steam deck