very interesting post this,
Im not going to represent any one style with my views, as im losing faith in 'different' styles, systems maybee but we each have our own 'style' after a few years training.
when I started I was taught the standard double hip, pull back, drive forward. big movement. (think reverse punch is best)
then i progressed to the triple hip, pull back, drive forward, pull back. Basically the whip principle. it became much smaller movement, far more 'impact'.
then I incorporated tilting the pelvis forward, making the spine straight and 'sinking', with slightly bent knees. which I now believe is proberly the start, during and finish position, with hips square ish.
Now thats alot going on in reality and all I can say is that the power generation method is alot smaller than when i started and relies on correct isolated muscle tension and relaxation as well as body structure.
Re the off balance theory, im working on that and am on the fence, so I train as i was taught which is keeping a good centre and moving with from the hara,
However my understanding is that zenkutsu dachi is 'front leaning stance' im fairly confident that small leans are involved and stances just stop us falling over, this puts a whole new aspect into body movement and power generation.
what also supports the 'lean' method is whenever I naturally try to put force or energy into something, think pushing or dragging then I lean into or away from it and use my body weight, again an interesting slant on karate mechanics, this maybee a significant difference between budo and bujutsu if you catch my drift.