True. I probably would have asked for held and rotated his entire body. Since we weren't there we don't know all the finer details that determine just what is the better choice.
Rotating his entire body might have been difficult with two broken femurs. This might have caused him to thrash around from the pain, causing even more injuries.
A number of years ago I stopped to help a motorcycle rider who was hit by a car and was lying in the middle of the street. Although he had a compound fracture of his right leg and a fractured arm, he would not/could not lay still, because he was lying on broiling-hot asphalt in August in Houston. He had a helmet on, but the faceplate was broken so I could not his face. But he was screaming in pain and throwing himself around.
I was about to the point of moving him to the grass on the shoulder, when someone came up with a large piece of heavy cardboard. Holding his helmet as still as possible, we moved him to the cardboard and he settled down.
When the EMT's got there, they started yelling at me for moving him. But the cardboard guy came to my rescue. Turns out he was an off-duty EMT, and he explained to them that I had done the right thing and why.