The game seems so ridiculously gaffed I wouldn't be too sure the middle thing even matters. Not saying you're wrong or right - I have 0 clue.
Early in the game it might be safe to assume that the diagonals are worth 1.5x as much as any other spot. I guess it can't be predetermined from the start as to what happens, so there is likely always a chance for any of them to go off. Even if there is some trigger function, the diagonals should be 1.5x more likely to hit.
Is the game without the visual keyboard and progs the same as the one with the checkable keypad? Just a different button interface?