I'm not an expert skiier but I'm wondering if conditions play a part in turn shape. Does the expert skiier say, "soft, ice, whatever, I'm turning where I want." Or is it more like, "I know my skis will respond better if I turn here rather than here and I'll vary my turn shapes accordingly."
Well, I think an advanced / expert skier can turn whenever / where-ever they like.
To me, part of what differentiates "expert" from "advanced' is that the former is looking far enough down the hill to be able to plot a line that avoids the worst of it. An expert's turn shapes and rhythm are constantly changing to take advantage of where the good snow is. Great skiing (to me...) isn't banging out a metronome-like pattern of turn shapes all the way down the hill.
There's a big visual difference between turn-traverse-and-look-turn-traverse-and-look vs. planned-all-along-changing-turn-shapes.
I try to do the latter... I intentionally try to not ski on the icy stuff unless there's no other choice.