could be, maybe different salt contents also. I would wonder if wrapping the meat tightly as opposed to my just covering the meat lug with 2 hot pork butts may play a part in it. Mine will have more moisture gathered at the top where the meat contacts the foil.
Not really sure, when I first started actually noticing it, I just figured salt is corrosive and it is even worse on aluminum when it is wet, factor in the warm humid environment I just subjected the foil to and that caused my pin holes.