The biggest mistake I've seen in amateur skiers is the downhill ski sliding backwards. So, for example, while turning left the right leg falls back and creates instability and bad posture. Instead, push the downhill ski forwards just after unweighting yourself (pushing down on the surface of the snow with your legs before initiating the next turn), such that the configuration of the two skis resemble that of a snowplow turn.
"When I win the lottery I'm gonna buy a mansion and name it "theabortionators estate" you can come an go as you please. Ill have a motorcycle in the garage you can run into a tree" -Kevtron
He's correct, to a point. Bringing that downhill ski forward will drive the turn, creating a more powerful turn. I hear this from race coaches a lot. It shouldn't be ahead of the uphill ski, or even equal.
As for the video, let's not forget that having a good foundation in skiing is incredibly important. Too many park skiers today can't do shit out of the park.
Your right. I was taught to ski like this after I had already been skiing for about 12 years, and although it's a little cumbersome to ski like this at first, eventually it clicks and it allows you to ski so much faster in just about any situation. As annoying as racers may be, they know what they're doing, so it definitely doesn't hurt to take some technique from them every once and a while.
Maybe I'm misunderstanding, probably, but I typically will stagger my uphill ski ahead of my downhill ski when I'm turning so that my hips are more pointed down the fall line. And then I will sort of switch that stance as I'm initiating a carve until im going the other way. I really don't even try to do this it just happens. For me it keeps my hips and shoulders pointed down the fall line, and I keep my hands kind of as if I was holding my poles like a kyak oar so that Im always squared up. Maybe this makes no sense but it works for me, so whatever.