Very intresting I would assume sleeping on your back would be better for “facial symmetry” then your side.
Wondered this myself. Facial asymmetry is an interesting one I haven't done enough reading on but I suspect it's got more to do with the poor diets, poor chewing habits and breathing and oral habits. Can't comment well at all with my current knowledge. But I intuitively agree with you. Would make more sense to lay on your back than on a particular side most of the time all night for your face to form symmetrically.