|the fundamental implication that I read here is that retraction turns are the order of the day for me on these skis. Are there conditions for which that would not be the case?
Certainly there are, Steve!
Because deep flexion is not a relaxing or particularly comfortable position to stand in, I suggest that we should not ever
flex unless there is a good reason for it. As my posts above describe, there are many good reasons for it in skiing. But there are also many times when I don't need, or want, the retraction turn movement pattern.
First, "air" can be fun! Just like springing off a jump or a bump, rebounding out of a turn can be something you do on purpose, just to play. Occasionally, it can even be an important tool, helping you jump over a rock or a snowboarder, or something.
In your video turns, you often displaced your skis to the side and/or redirected them during the "light" phase after the rebound. You didn't want to have to do that in those turns, but there are times when you do want to, or have to, redirect. Watch World Cup races, and you'll see it often. Sometimes they retract through the transition, trying to carve as close to arc-to-arc as possible. Other times they explode "up," followed by subtle or powerful redirection of their skis before reengaging the edges and carving.
And sometimes you just need to hit the brakes!
At low speeds, two things happen. First, the forces are not as dramatic, so neither are the needs to manage these forces as actively. You aren't going to get much air over a bump at 2 mph, and you aren't going to get "popped" out of a turn at that speed either. So you might as well take advantage of the opportunity to stand up and relax for a moment through the transition.
For beginners, rising out of a turn can help reduce the edge angles, facilitating the all-important edge release that starts a modern offensive-type turn. I am still very cautious about this recommendation, though, because ultimately, "releasing" belongs in the edging/tipping movement pool, not the pressure control/flexion-extension pool. Tying the movements together by suggesting "extend to release" (a very common direction from ski instructors, I'm afraid) can cause exactly the problem move we're trying to eliminate in your video turns! It also causes confusion in mogul skiing, which requires a very active "retraction turn" movement pattern. At the very least, if we must
teach "extend to release" (I don't), remember that it must be an extension out
of the turn (finishing neutral), not an extension to start the next turn!
If you wait until it's time to start the turn to begin to flatten your skis, with or without an extension, it is too late!
Second, at low speeds especially on steep terrain, the ability to carve the upper part of the turn is far reduced, so you actually have to guide the skis through much of the first half of the turn, until gravity adds enough pressure to bend the skis and carve. Some "unweighting" here helps, although it generally doesn't need to be any sort of exaggerated "up" movement.
In freestyle skiing--jumps and half pipe--where you're basically trying to get air and often throw yourself into a spin as well, extension and upper body rotation are the keys!
To me, though, in clean, linked, offensive turns, I think of extension in the transition as a luxury. At low speeds, in particular, I can often get away with it. But the more dynamic (greater speeds, steeper slopes, tighter turns, stronger forces) and challenging (moguls, crud, etc.) the skiing gets, the more I can't afford the luxury. Speed magnifies everything, so the higher the speed, the more actively I must manage the pressures with often vigorous flexion-extension movements. And the more sidecut your ski has, the more touchy they are to all these things as well, so those little Metrons don't give you much time to relax!
Finally, other than practicing or demonstrating, I don't usually make a conscious choice to use either "retraction" or "extension" turns. Retraction and extension become unconscious reactions to manage the pressure of turns moment-by-moment. If the terrain drops away from me at a transition, I will unconsciously extend my legs to keep my feet in contact with the snow. If the transition occurs on top of a bump or roll, I'll unconsciously exaggerate the retraction,
again in response to (or perhaps anticipation of) the forces at the moment.
Ultimately, flexion and extension are a skill, not a technique. They're the movements of the "Pressure Control Skill" of PSIA's "Skills Concept." Expert skiing requires the ability to flex or extend in any or all joints, at any time, as needed for balance, pressure management, and direction of the body's momentum. We practice all the specific forms and timings that these movements can take, but practicing and real skiing are not the same thing!