"If that's a "natural movement" that "just happens", why is over-rotation (the virtual opposite of over-countering) what just about every novice does, before being instructed to do otherwise? For many of us, counter is done because we're taught to do it, and it's not what comes naturally. In fact, to us athleticly un-blessed types, a LOT of skiing is counterintuitive, and we need to work, and work hard, at learning to do what does not come so naturally. By way of example, while trying to balance on one ski in learning the White Pass Turn, I "naturally" faced uphill - and seeing that, Bob Barnes instructed me to face toward the ski I was on. That sure works better, but it definitely did not come naturally or feel natural to me."
Enter the muscle geek!
The obliques have two functions; One is dynamic rotation of the torso, the other is dynamic stabilization of the pelvis. Of the two, torso rotation is more commonly used in daily activities, and thus feels more natural.
As for the stabilizing function, note the emphasis on the word 'dynamic'. In other words, by stable, we do not, in this case, imply "locked". Its more like a stabilzation of optimal alignment, as opposed to a lack of movement.
Do you recall, at the academy, I demonstrated an exercise involving being seated on the stability ball, and walking from one 'cheek' to the other, while keeping a relatiively stable upper body. This was to show how the obliques work as stabilizers, as opposed to rotaters.
On the bump thing, as a newbie bumper, i find that bumps are a combination of reaction time, as well as strategy. Do advanced bumpers use less strategy, and more reaction?