No I really think it’s a bug. The only string that appears to work consistently is F43.
So if you do F43 into the low and then follow that up with F43 into the OH, the KB will trigger.
Believe it’s supposed to be designed so after you do the low from NS, the NEXT attack from NS must be the OH. In other words you should be able to store it if you connect the low, go on with the match, and then when you do NS again you can get the OH crushing blow so long as you don’t do another low or cancel or command grab.
But like I said, only seems to work when you do F43 prior to the stance.