Gives some thought on facial asymmetry but I think we use the musculature of the left and right in different ways. The right side of my face so dominant that the left does not exist independently for most practical purposes.
If I grab my right wrist with my left hand and write in script with my right hand my left shoulder becomes passive. However if I grab my left wrist with my right hand and write my right shoulder/arm still tries to dominate the script even though the left hand has the pen. It is hard for my right arm to be passive because of it's dominance and habitual experience of writing . I believe the same mechanism plays out in my tongues and faces. My left subordinates itself to my right giving the illusion of one tongue one face.
I am almost infantile in the use of my left face tongue in an independent manner.