It's the reverse 214B off of 5[C] thing (where 214B puts them behind you); too unsafe/unreliable imo
Ah, that's actually completely reliable and useful for a reset opportunity though. Because you basically have a guaranteed combo off of 214b 5b 5c launch etc.
That kind of situation would more likely confuse your opponent. Depending on who you are up against, whether or not they have a tendency to mash plays a significant role in how you should handle this situation.
If your opponent has a tendency to mash buttons, a delayed 5b should net you a counter-hit reset. However, if you are playing against someone who tends to block more, an overhead right now would be the most appropriate way to ensure a reset. If they start to see it coming, 2C is also a viable and fairly safe option even on block.
Of course, this all assumes you know that it's coming. If you don't see it, or you're not sure if it's going to happen, your best bet would be to do a 5b hit confirm into combo depending on which side they end up in.