Sometimes they're flailing. Or they appear to be in control, except that their eyes are bugged out in fear. They just don't look like they belong where they are. Jensen says there's a big difference between skiing too fast and skiing out of control. Their turns are not consistent.
Speed is an element that comes into question.
If an experienced skier is cranking down an empty run on the mountain, there shouldn't be a problem. Add a couple hundred people, and it's not safe. But introduce speed and the dynamics come into play. It's a bit like playing Russian roulette. How the dictionary defines a word and how the law interprets are often slightly different.