I've never needed anything mystical in these kinds of things. The mechanics alone are sufficient to explain the effect. I still often refer to it using the ki vocabulary, but my students learn first that ki is just a shorthand for a certain type of mechanics.I agree with everything you said. But I ALSO think that in Hapkido, when you open your fingers wide like that, you are allowing KI energy to flow through your arm from your center. When you combine the mechanics you mentioned with the belief that KI energy is flowing through your arm, you get an even more powerful technique.