Yes, it's' more or less this. Many poisons can affect the brain, and in particular cause its tracking between (say) balance and the visual system to get out of sync. The best survival response is to get rid of the poison, hence vomiting. So it's not the ear per se, but the brains interpretation of different sensory inputs. That's why you get sea sick ..your ear is telling the brain one thing and your eyes another. Same for too much alcohol. Kids are more susceptible as they are less tolerant (another survival thing).
So when you look down in a car, the car body and (e.g.) book is telling you that you are stationary, but your ear says you are swinging around, and yeah you get sick. The best mitigation is to look out the window AHEAD of you, so you "see" the same thing your ears are telling you. Same thing for sea sickness, get on deck and look toward the bow of the boat at the horizon.