That's not that simple. You can want to do some thing when the entity jump, like play a sound, an animation, or whatever.  That an event for when an entity jump.

In my case, I need to know the entity jump capability, at some time in my mod, and I don't want that that entity to jump. So I need an other event (because some other mods may want to boost the jump capability of the mobs). So there's probably some change to make on my new event, but I don't thinks we can merge them, they have not the same purpose.