So when do you think they should have stopped?

It is very strange that there is no damage on the rest of the wheel and even the wheel weight is still there. For that to have happened the wheel had to be locked up solid. When I first saw the picture I thought the tow truck driver had to have done it and just kept dragging the van until the tire was gone, then the rim was ate up too.

Nope, not locked up at all. A used wheel and a new tire and they were on their way. It is icy on the roads from all the snow and freezing rain. I would say they braked at one point and locked the wheel up and it could never gain enough traction to start spinning again.