Immortal
Blind justice....
Only a VERY late ji2 guarantees OH (and obviously low), if you use ji1 or f1 they can simply backdash of anything you do after, neither low or oh wont catch them and you will get rekt on whiff (althou full oh string without canceling will catch shorter backdashes). People just respect jip1 thats why its working but in reality it doesn't guaranty anything, same as f1.We had a big discussion about this a while ago and the conclusion was that ji2 (not ji1, it's got less hitstun) is the only button with enough advantage to force them to block both the oh and low 50/50. I'm not sure if it has to be a late ji2 or if you can do the ji2 after b2 and still get the vortex. With f1 and b2,b2 they can backdash or armor out of both or at least 1 option. Backdash is easiest, because you can buffer it. You can't buffer specials out of hitstun, so it's incredibly difficult to armor on frame 1 although possible with practice.
There is obviously a little guessing game here coz after the f1/jip1 you can always go for f1,2~leap which will catch even the best backdash in the game but in reality its usually a waste of dmg or reset potential.