Its a matter of RAW vs RAI. In this case I think Anthro is right about the RAW it doesnt always make sense but RAW is what it is. Would a sensible GM impose limits on how non-lethal works? Probably. But there is a lot of language among feats and other abilities that support the nonlethal as a seperate type conclusion. Nonlethal substitution being the most clear in terms of the language used. In fact nonlethal substitution looks to me as though it explains RAI and reinforces RAW. That wording was looked over and accepted by the editors. Seems pretty clear cut. And as always Specific trumps General.