That’s hilarious but I think there is some validity to it. Somehow your playing has to hook up with your body and emotional body. We play with our fingers, mind, emotions,ears,and muscles. I’m a piano player and I can think of one piano player in particular who goes thru quite a few contortions plus vocal noises (Keith Jarrett) in order to play incredible music. And of course everybody has seen BB Kings great Guitar face. I say whatever it takes. I’m sure there are some that are stone faced and still, that can really wail, and maybe some who just fake the facial contortions, everybody is different and people play with different ratios of Fingers, mind, and heart.