[Ref Devil]

It's a rule. It was called last year but I've seen a lot of kids jumping over other kids and not many calls.

If I understand it correctly it is discretionary.

Its definitely not discretionary. Its a written foul rule, just like holding, personal fouls, interference, etc. It should be called as such, shouldnt just be ignored. It is usually a highlight play if pulled off but it is also an extremely dangerous play if interupted. Definitely needs to ve called while still in the rulebook.