yes skiers assume the risk. But Deer Valley isn't really a ski hill. The hardest runs are equivalent to beginner -intermediate at say Snowbird or the Canyons, and they are all beginner compared to Telluride or the bowls at Sun Valley.
Most avid skiers pick somewhere else. Snowboards and celebrities have ruined skiing, and the term fall-line skiing. The better the skier the more time you sit on a chair, or riding the tram.
The etiquette of skiing says the up hill skier is at fault. No way is the up hill skier going to hit the down slope skier if the down slope is going faster, and if they are going slow or stopped, the up hill skier can turn to avoid them.
All the witness stuff is just trying to get around that. Control the words control the narrative.
