I do find it weird that the minimum suspension for spitting at a ref is twice as long as for assaulting a ref. That seems a bit backwards to me.
(and to be fair, I've probably deserved to be assaulted after some of the shark games I've had in the middle hah)
I'm guessing the lower minimum might be because assault could cover anything from a slight push to being whacked with a baseball bat, whereas spitting at a ref is spitting at a ref.