As someone who grew up constantly car sick, the thing that always got me was "unexpected" changes in velocity -- usually applying the brakes but then releasing it unexpectedly.My SO complained of this, we have deduced that in her case, it was occurring during the regen braking. When we switch to low she notices an improvement immediately.
So, I can see how an unexpected "drag" on the car, from regen, would simulate this in a modern EV, especially if the driver constantly lifts their foot off the pedal and then back on. Off. On. Getting me dizzy thinking about it.