N3DS face tracking is only used to correct the stereo separation (so each eye sees a separate image without having to be exactly on the center), not to move the scene depending on where you are. So if you have a scene like in that experiment, you would see it skew to the opposite direction you move your head. Also the vast majority of games don't have that much depth anyway, even at the highest setting, probably because the scene doesn't move accordingly and would make people dizzy.