Since the document is back from 2005, and there seems to be no documentation of it on the forums, I would assume it was either planned but not released, or possibly in place at the starting age of toribash, which I doubt.

To answer the question of why it shouldn't be a thing, is because this game is pretty balanced (as far as tori and uke go), the addition of powerups would probably lead to TB becoming a pay to win game, something the majority of this community does not want. Would you like it if you were constantly destroyed by some guy who has power ups? I sure wouldn't.