A double strop is probably a good solution but then again maybe not if the stretcher is rulled because of trees. I have used strops, that come in different lengths without crotch straps for 30 years without a problem so realistically a single strop should have been no problem assuming that it is correctly placed.
We lift people a similar distance from the road because the terrain is too difficult to be carried over leading to a greater probability of further injury from the rescuer falling over and dropping the casualty.
Bottom line is that you cannot critisize what the guys did going on the information in this report, you have to be there I guess. Without seeing the clearing, how the strop was placed or what the casualty did during the winching, it is unfair to judge; but of course some will.
Flying helicopters can be dangerous, winching is always dangerous, it is just balancing the risk against the gain that is the tricky bit. I feel sorry for the crew because someone will use 20/20 hindsight against them.
Heads Down, look out for the flack.