Board Thread:Theories and Speculation/@comment-1458758-20190708202646/@comment-1458758-20190709072637

Except Tobirama was a vicious pragmatist. If the immortal warrior he summoned wasn't putting up much of a fight or was on the verge of being sealed anyway, releasing its spirit as a final assassination blow, or using the newly possessed target to attack as a sort of living Edo would serve his purpose better. And again, we know he has a technique similar to Dan's by his own admission, but is for some reason a kinjutsu. So the idea that its part of the arsenal for edo tensei, even if he never made use of it would make sense to me.