Re: Baseline skillset
Heres my take FWIW. Ballet dancers seem relaxed too. Often what we perceive as relaxation is really a flow of well-connected tensions rather than a lack of tension. When Tohei does a vertical "spring" action, you can see his legs compressing actively (he wouldn't need to make it visibly so, since the essence is not in the joint articulation), but his chest would be doing something similar (either as a result of the legs, or in conjunction with), which is less visible. Since that power moves the arms and sends energy into uke, he doesn't have to do any isolated and overt arm/shoulder motion. So he seems relaxed. Except for the parts that have to power the entire system, that is.