Dunno about a 'waste' of time--but it seems misplaced to me. Butt doesn't (or shouldn't) need additional moisture. The issue to me is one of flavor and texture. Since in most cases we're talking about pulled pork rather than sliced, adjusting flavor and texture is far easier to do, quicker, and more effective, imo, if done after the pork is cooked and rested--while it's being pulled. No fuss no muss. Just my two.