When you walk, run, climb a ladder etc. you move right hand with left foot and left hand with right foot. The same goes for rope walking.
The earlier petzl (handled) hand jammers were right handed, so naturally connect by the foot loop to the left foot. Hence the right foot Pantin.
Now that petzl make a left handed jammer, the left foot Pantin goes with it.
This only really matters if you use the "rope walking" technique, if you use the "fogging" technique it makes no difference which hand /foot you use in terms of progress up the rope, so whichever is more comfortable wins...