Most victims in a tree well have a good portion of their body on the surface. There is very little potential hazard in approaching the victim to remove skis and assist them to get upright. Imagine a person in water with their feet suspended only a foot above the surface. That person WILL drown. A tree well is hazardous in the days immediately following big dumps of cold snow. The depression is invisible from the surface, and the victim falls in, with the head and shoulders below the hips. Snow collapses around his head and suffocation/panic begins. The skier has been exercising at high altitude just before the accident and is usually breathing heavily. Imagine, there is suddenly no air to be taken in because the mouth and nose fill with the perfect seal; light crystalline snow. If the snow is so light it can't be packed, it is difficult to clear an airway, even if his hands are free. If that clear airway cannot be established, the victim will have only moments of full strength to release skis, climb the branches or take some action before consciousness goes, and about 10 to 15 minutes to be extricated by a partner. All of this, and the guy's hips, legs and skis/snowboard are still at the surface. Quiet deliberate movements to create an air space are usually better than vigerous struggling. Try to remember that when you are drowning in snow.
I was skiing with a guy on a snowboard and we went over these tiny tips of trees emerging from the snow. They looked like little sapling, but we were on a 20 foot base in deep powder. He tripped and fell head first next to a little tree top, and couldn't get out. It looked funny at first, then got serious real quick. In another case, I watched a guy huck huge off a rock into deep pow. He augered in, and it took six of us to dig him out. And then there is my close escape from a tree well written in a thread somewhere. Tree wells suck.
A less lethal problem is entrapment in the funnel that forms around trees after snow has consolidated. This might be a scary place, and difficult to get out, but it is not the kind of tree well that generally kills.