UPDATE: According to Webster, a tautology is a repetition of the same meaning with different words (the "どうごはんぷく" is it too), whereas "Those who are dead are dead" is the use of the same words to express a non-redundant meaning (that those who are dead should remain dead -- hello DBZ -- to say more would be a major spoiler (ok, here's a good spoiler: Yoko lives)). One can say it's the opposite of a tautology.