so why wasn't the evil containment wave used on super buu when the world was obviously nonpopulated? buu doesn't know the reversal technique and Piccolo knows how to do it. the situation marets this kind of action. and the notion that super buu wasn't pure evil doesn't make sence because goku on supreme kai's planet even said that he hasn't felt this much evil in a being before. so other than to push the naritive why didn't piccolo use it.