I have looked at a few of these, and I have never seen one with that added tooth piece. That thing with the teeth looks like it is there to perhaps augment the 3PH lift force. It goes on the 3PH with the "V' on the bottom pointing to the rear. It might be that as you back up to the tree that toothed foot/leg drags behind, and as you pull forward the whole assembly tries to polevault up over that leg. But I would think pulling forward would loosen the bite of the "V" into the tree trunk, so that dosn't make a lot of sense.
Perhaps it was designed for use with a hydraulic toplink. Once the "V" is engaged, you retract the hydraulic toplink and the whole assembly pivots and uses that toothed leg as a fulcrum to pry the rootball upward, kind of like a "T" post puller does.