For the love of god, you Americans are so paralyzed by fear of litigation.
The salient point in this query is that its a wilderness type situation (more or less) not an urban or rural situation. Clearly, its not ideal to have this pt walk out, but the situation may dictate some form of assisted ambulation on the pts part, where no weight is put on the injured leg.
As the OP states, this happened 400 yards into a cut line, so obviously this is a industry job of some sort (pipeline or logging operation likely). Typically, this means there is one responder and a truck camper used as an ambulance which may or may not be equiped with the proper equipment for this type of rescue.
So, no a pt with a leg fracture should not, under normal circumstances be "walked" out, but sometimes the circumstances dictate a modified response. Additionally, it sounds like the OP did in fact find a safe solution, although apparently, using a quad is the "lazy" way to do things. However, one should pause to consider the wisdom of four men hauling a heavy cot the length of 4 footballs fields over rough terrian thats lousy with tree roots, and other debris.