But we DO have a horse (ma=horse).
You are taking the analogy beyond -- with angles, etc. -- what I was using it to illustrate (power).
When we hit, we hit with our center (think of it as a solid vertical beam or column of mass in our bodies), so that we strike, we actually are hitting with that beam/column into the opponent's vertical beam with our arm simply acting a a conduit (like the lance in the jousting analogy or the stiff-arm in football). It's not the arm that powers it, and hip rotation doesn't strike with your center but rotates around it. If you grasp this way of striking, you see why functionally we punch in the center, why the punch is straight (nothing to do with the shortest distance crap),why the elbow is down, why the fist is vertical, etc. And, you'll see why it's nothing like what a boxer or kickboxer does.
Yes, the hip is involved but the power doesn't come from the hip but from our center driving into our opponent (we can't move without involving the hip). The body (our center) is the hammer and our arm the nail.However, our horse must drive the punch from the ground up. I mentioned shifting and stepping too, since I interpreted your previous post as saying we stand in a YJKYM stance all the time including drill and chi sao. Since the opponent may move then we must be able to respond to that. Or, I may want to take a new line, depending on the situation - this may require a shift or footwork. I was not talking specifically about the punch. So that's my fault if I went off on a bit of a tangent.
From my perspective, YJKYM isn't a "stance" but a horse, a way of using our body. You can step, turn, etc. and still use YJKYM. YJKYM is the hammer.