Example from AttackEntityCallback, but applies to everything else in that package too:

Might also be a chance to have a few more effects, depending on what is required? E.g. swing hand on client but don't send a packet to the server. We would consider the unused results "undefined behavior", hence it would be fine to give them new behavior.

I think this can be considered a feature at this point - we can add more meanings to the event in the future thanks to this.