Ok, I had that post a while back about out PMTS'er's tighten an arc. Leg steering came up, and I never felt I got an actual answer that made any sense as to how that would tighten a carve.
Now I have found a logical answer that makes some sense.
In Witherell's book the Atletic Skier, he makes the statement that applying steering (which he defines succinctly as a pivoting force applied to the foot) while in a carve will tighten the radius of the turn. This is much like others have said but never with the why. When you look at the whys many said, the oppisite is true - as Jay pointed out, the heel will go flat so edging diminishes.
Anyway, Witherell points out that the pivoting force on an inclined edging ski is always to the base of the ski, not a perpendicullar to gravity pivoting force. So, when your in a carve and banked over with your ski edging, when you add a steering force it simply makes the tip of the ski pressure down into the snow harder. Thus, you aren't really pivoting or adding pivoting to your turn as that is in the up down directcion.
This may not be what people mean when they are talking about this, but for me, this at least has some logic and passes the "smell" test.
I'm not sure how relevant this movement pattern is now adays as this book was written in 1993 before shaped skis. The need to make sure the side of the ski at it's tip is in contact with the snow that Witherell felt some steering helped maintain while in a banked carved turn, may not be much of an issue on todays much shorter shaped skis.
I found it interesting that Witherell made a complete distinction that steering was to rotate the side of the tip down into the snow and not to in any way directly "rotate" the skis in the turn.
My question would be for people advocating this "legacy" movement pattern.
1. Is this needed anymore on shaped skis?
2. Are people taking this old adage and not understanding it and thinking Witherell meant rotate the skis with leg steering?