I must say I disagree with you. Before going to such esoteric concepts like Ki, if it exists, students have to learn pure biomechanics of the technique. It means, how to create multiple leverages on different joints, then how to control and turn the hips of attacker with these leverages, next how to unbalance him and maintain this unbalance whole way down.
Indeed...but in a sense, there are no "pure biomechanics", or at least, no universal ones. If you've got small hands and uke has enormous blacksmith wrists, your biomechanics will be different than vice versa.
I'm remembering a class at summer camp where I got a small, wiry yudansha with small hands and wrists to show me his "nikkyo with big people" tricks