don't you mean left/right bits? (of course I'm aware that the center bit isn't the real core, but I want to avoid confusion)
there are two attacks used by the bits when defense is up (as you said). one is B2, A2 (where it spins you), the other is B2, 67, 8B x2 (where it hits you and teleports away). based on the tech list, these attacks must be erase and tragedy (negate and obliterate on DS), the problem is, which is which?