JB and Max....I would agree that using rotary movements may not be THE tool to use in off piste skiing...
But I gotta tell ya...I've skied with some pretty darn technical skiers and if and when you're in a tight chute or tree section, a rotary turn (think twisting) the lower body to change directions can be a handy tool as well as a survival tool. Visualize having to make a quick turn on a steep nasty icy snow condition in a 5 foot opening....heck even dropping over a cornice that an air entry is not on todays menu....one might sideslip over the entry moving in one direction, not like what I see and just pivot the skis due to rocks or whatever in the other direction....someth ing I've personally and rarely ever had to do.
This may not be the preferred way to make a turn..IT"S JUST A TOOL......having many tools in ones ski bag is a good thing in building all mountain confidence.
For many of us, we are talking about highly dangerous and technical terrain that we seldom if ever ski in...but knowing that you've got a back up skill that you know how to apply...."it may not be pretty" but it get's the job done! Best, g