How come virtually nobody talks about the apparent cross under, crouch jab anti-air people do?

Current Fighting Games Fighting Game Discussion
1

I’ve seen it multiple times. A player would be positioned particularly close, predicting a that the opponent is going to imminently jump. When they do, they walk forward slightly and crouch jab the opponent’s cross up. Can more experienced sf players go more into detail about this mysterious phenomenon? Thanks.

2

What’s so mysterious about it?

3

I think the fact that the ts get caught with it everytime must blow his mind