I'm fascinated by the questions. Fools rush in where angels dare to tread. Great minds have so far either dodged the questions or kept the answers to themselves. So I'm rushing in here, principally because I hope it will stimulate you or others to provide their insights into the questions you posed and either confirm or critique my observations/guesses. First, I'm assuming that this montage is the one you were referring to which Bob Barnes posted earlier:
I apologize if I am breaking any protocol in using the photo he posted in another topic. After you asked those questions I have spent a long
time studying that one montage. It appears to me that in the first three frames from the top Herman Maier is extending his uphill, that is outside leg and the inside leg is being guided toward the outside. With the inside leg and foot now closer to the outside leg and foot, any movement of the CM to the inside, increases more dramatically the edge angles of the skis than if the stance were wider. Somewhere between frames 2 and 3, when the feet are the closest, he appears to be close to the three neutrals, tip lead, edge angles and weighting. Beginning at frame 3 he is moving his CM toward the inside of the new turn. About frame 7, (one frame past the gate) it appears that the inside ski is beginning to be guided more to the inside, increasing the seperation between the feet. I can't really see what he is doing in frame 7, but by frame 9 there is clearly a substantial amount of seperation. By about frame 14, (about half way between the two gates)the inside (uphill)leg is noticeably extended. In the next frame it appears that the downhill leg has flexed, lightened and moved toward the uphill leg decreasing the seperation between the feet. [Note that the last frame of the montage and the third frame of the montage are practically identical, so much so that one could almost believe that the last frame is simply an enlarged version of the third frame. He certainly is consistent.]
With those observations let me go with my foolhardy attempt at your questions. First, the changing seperation occurs by steering the inside ski toward the outside at, or just before, turn initiation and then back to the inside during the control phase of the turn. I don't think the movement of the CM toward the inside serves to help "pull" the inside ski toward the inside -- not at least as I would understand the word pull. Pulling the inside ski would imply drag to me and my assumption is that the racer does not want drag. The movement of the CM to the inside might facilitate steering the inside ski toward the inside. After studying these, my guess is that the stance is narrowed for turn initiation because from a narrower stance any movement of the CM toward the inside of the new turn is going to have a very dramatic and immediate effect on the edge angles. Once the turn is initiated the focus in the control phase of the turn changes to one of stability in dealing with the rapidly developing forces.
Are these plausible explanations for the observations? Help me out, I have been inexplicably fascinated with the questions you posed.