I don't agree with your premise that full share = annihilation.
I would argue that the full share is a compromise between annihilation and assassination. therefore, it should exist as a legit option to play with.
also, the replay you shared doesn't prove anything. I don't have the statistics ready but I imagine that most of the time when an entire army goes poof! . the game collapses quickly after in favor of the team who scored the kill.