gongfuren
Arma Virumque Cano
0f gap (aka no gap) exists because the active frame of the command grab happens on the first possible frame after blockstun. The defender is able to input something because the blockstun wore off, but the grab goes into active frames in that same frame. Think of it like a meaty attack, where the defender's first possible frame to input something is also the frame in which an attack is connecting with them.Well the first one at least is incorrect, there's no such thing as a 0 frame gap. 1~sun choke has a 1 frame gap because you can backdash it since backdashes have at least 1 invincibility frame at the start of the backdash. Also how did you come to the conclusion B1~DB2 is a 2 (or rather it should be 3) frame gap?
Backdashes are invincible on the very first frame. Therefore, if you input the backdash to go off right when blockstun wears off in a 0f gap tick grab situation, the backdash will immediately grant the defender invincibility.
2f gap calculation is in my post before: https://testyourmight.com/threads/how-do-kotals-tick-throws-work-even.62692/#post-2221066
There are 2 frames in which the grab is still in startup (not yet active), but the defender is not in blockstun.