I'm not sure how many of you have a children's accreditation but keeping the kids forward is not where their body would balance. The proportionally large head shifts their stance aft. We see this as blocking in an aft stance all the time. As they grow all of this changes but suggesting keeping them out of the back seat ignore the fact that they are still developing and an aft stance is actually where they would find balance.
The shoulder is an upper body rotary move TDK. They are trying to add rotary from there instead of from their legs and feet. why? Usually because the ski is not releasing or turning fast enough. Which is a sign of being too locked up on an edge.
Epic, I would say what you described is a Wedge Christie since the edges do not remain opposing. One of the descriptors is that they do remain in opposition throughout a wedge turn.