I did a little more testing today. After a NH GS A, if the opponent does a backstep to realign themselves and then G right away, their out of range of flapjack. However if you do a step grab or step flapjack in anticipation of their step, they have a short window the react to whichever one you did. Though i think its still possible to react to one or the other.
Silent, I wish the move didn't have all of that pushback. It was so much better in the previous versions :(
Do you mean as a techtrap? If so, I think FC 3B would work better to catch left techs, doesn't cost meter and does more damage. Also the opponent can block GS K BE if they just guard :(