For the record, PS moved to the newly discovered BW damage formula a while ago:
http://www.smogon.com/bw/articles/bw...damage_formula
I'd imagine that before that change, PS (using the gen 4 damage formula) would be emitting mostly 4's, too. I'd also imagine that if PO is emitting 4's, that's probably because they're still using the gen 4 damage formula, not because they have the correct formula.