Skiing dynamically means limit folding at the waist even for expert skiers.

Hip Collapsing robs angles, ski bend, and tip engagement!

Even expert skiers can be seen collapsing their hips to reduce pressure. When the timing and correct movements of leg retraction and counteracting aren't coordinated or are miss-timed that's the result.

This is an expert skier, however, this skier is giving up fore-aft balance and power because the timing of collapsing the hips is too early. This reduces tip pressure and also moves the hips back on the skis. 

 

If you look at the outside right hip it is open and there is no folding or lowering from the hip. The hip is driving forward to keep the tip leading the arc.

Here you can see the change in hips more extended to hips more collapsed. This results from a lack of counteracting of the hips or staying too square to the skis.

The comparison shows the obvious benefits of keeping the hip and torso up and driving forward. The result is more power in the ski, more tips leading the turn, and higher angles.

Again notice the left hip Counteracted, this gives you more control of the turn and more versatility for a change of angle and turn size without skidding.