With your example, we are getting into the idea of a technique. A technique might be to relax all of your backside, and lean against a person, that might be a good or bad technique, but it's not the body use specifically.
So if you are "everywhere beforehand" so that you never have to react, how are you not using a huge amount of energy? Are you saying with being "everywhere beforehand" that your body is always working?
And it's not really a technique. That's a macroscopic example of something that happens even at the level of the microscopic. Physical interactions are rarely clean and forces are rarely simple. A single push is not even just a nice straight push like they show you in physics diagrams. Another human being is not a spoon. They don't respond to pushes like a spoon - hell, they can actually respond, the spoon can't.
On the other thing, because I am using a huge amount of mental
energy, and because I am still a noob, I use a lot more physical energy than I need, though much less than when I started - I dare say I am becoming more physically efficient, but that is not expressly the goal. The goal here is to achieve a position of dominance. The quicker you dominate, the quicker you can return to be lazy and eating cheetohs lounging around on your couch. That's pretty efficient from the long-term perspective, not so much from the short-term perspective of the encounter itself.