You misunderstood my answer. By "vertabrate movement," i was referring to how movement works in all vertabrate animals, not the bones of the spine.
That little elbow ossilation is a tell tale sign that the player is moving naturally... more in line with how vertabrates evolved to move. And yes, it is more efficient. Not only does it feel more effortless, but it literally uses fewer calories. I'm sure you could see how saving calories and needing less food would act as a driver behind this evolutionary development.
As I said, coordinated multi joint movements and force production are complex. You can take entire university level courses on the topic and not cover it all. So yes, reducing a multi joint movement down to muscle A back, muscle B forward is laughably over simplifying it.
"Leave stroking to the subconscious" is the best we got right now.
Maybe one day someone will explain the details to yall in a book