Well, a falling tree can also explain the ravine 4's injuries.
The problem is, where did that tree go? Suppose the party doing the coverup airlifted a fallen tree by helicopter?
And according to that theory, only 6 of them were "placed" which I have to admit I don't fully understand yet, as that would involve one of the ravine four but not the other three.. So the tree must have fallen there? But who would set up camp in a stream?