The only reason to annul this touch is if the referee is saying that Fencer A caused the corp-a-corps to avoid a touch (the double from B). If the light clearly goes off before the corps-a-corps, I don't see this as a valid interpretation, as B wouldn't have made the lockout anyway. If the referee annulled the touch because he could not tell when the touch arrived, I understand but disagree with the call. You have to be certain of a reason to annul a touch not the other way around, IMU. The answer to your yes/no question is: no, in any weapon. That is nearly the whole point of having a scoring box in the first place.