Why do you both have such a narrow view of separation? Skeletal separation between the upper and lower body is indeed a key differentiator between the intermediate and the advanced skier. But don't pigeon hole it into just rotary based skills. The ability to separate lower body skeletal joints is also key to the creation of angles (angulation) which is critical to the carving process. Just as I see many intermediates using upper body mass in the pursuit of ski redirection, I also see many intermediates inclinating said mass as their inferior way to achieve higher edge angles.
Finally, and this is a pet peeve of mine, please don't tell someone that good/advanced skiing requires you to face down the fall line. The upper body faces relative direction of travel which is dictated by the radius of the turn assuming a turn is the intent.
Markojp, see how combative Jesinstr's post is? Maybe people can't see that? If JESinstr's post is the kind of fun talk on the hill to be had while skiing or hanging out in a bar, then count me out of your ethos. I never talk to friends that way.
My post was very modest. Separation is necessary for quick turns. Some people don't worry about separation much, because they don't do quick turns. How is that a narrow view? It's absolutely 100% true. In regards to advanced or intermediate skiing, if you read my posts, my main focus was that there are two paths people go down. One path is initiating turns with the upper body, and the other path is initiating turns without the upper body. I consider initiating turns with the upper body to be an intermediate technique, though I also commented about how these intermediate skiers can take their techniques to most marked trails in the country, so it's not that important in many regards.
Separation comes into this, because when an intermediate skier initiates their turns with the upper body, it's almost impossible for them to achieve the separation necessary for a stable upper body for quick turns. When does initiating with the upper body cause problems for non-judged situations? First of all, it causes problems with carving, but carving is often not necessary to get down a trail comfortably. The only time I see carving as necessary is when the snow is heavy and more than a few inches, such that the ski can't skid. I see intermediates, that initiate with the upper body, struggle in these conditions, but I've also seen these same skiers get on fat skis with rocker and shine once again. So, technology has narrowed the range where those techniques are ineffective. Next, these intermediate skiers that initiate turns with the upper body, can't make quick turns with stability in the bumps, though typically all they have to do is skip some turns. Any other times initiating with the upper body doesn't work on typical marked trails? I tend to focus on limitations for quick turns, because quick turns in the bumps are what I enjoy doing.