Have nothing to add from
@BGreen's post. Nailed it.
Different coaches and programs have their own thoughts on this SL vs GS training volume, and even free skiing on SL vs GS skis. I've grown up around programs where we spend a lot of hours on GS skis. But, not doubt there are some very well known coaches and Program Directors, who have produced exceptional athletes and believe that the foundation and base of it all should be SL. Free skiing, drills, all sorts of training.
Two years ago, Mikaela's youth {J3} coach, and her primary guru joined Ski and Snowboard Club Vail {SSCV} as their Executive Director. SSCV is a huge club, with which I have some familiarity. Before he joined them, they were the USSA Alpine Club of the year for something like five of the prior six years. If you look at results as a measure, they easily can make a case as being in the discussion as one of the country and worlds best.
My understanding is that Kirk and his new Alpine program director have introduced much of what he learned in his decades at GMVS and Burke, where his record of producing USST athletes is pretty much unparalleled. I'm NOT saying that it's "right", or that I follow this, but they have flipped things around to my understanding, so that the kids are spending far more time on SL skis. A much higher percentage f tie as U12's, and still the majority as U14's and U16's. Along with that much less time on speed at U14's and U16's. I think no DH until they are FIS ages.
So, that's a change and it's done with a lot of thought and planning, I imagine. I assume that it does have to do with the amount of turns, and the progression that can be accomplished in a concentrated amount of time. Certainly the concepts of Periodization and rest have worked for MS. I think that's more of the core programming at SSCV.
Now SSCV's training venue and hill space is world class to say the least. Amazing. All the resources you'd need to do anything. So it's not like any of this is dictated by time, hill space, lifts, etc. Not like Buck Hill, where having a program that grows out of SL skiing might make a lot more sense.
Can't help with the hip on the snow!!