what would it mean for one output to be connected to the same input, multiple times? At best, it's the same as being connected once, and at worst it is a crash waiting to happen, and inbetween, we have all sorts of undefined behaviours. Also, if you consider the representation, being connected once, or being connected more than once looks exactly the same, so it should really either be prohibited, or it should behave the same as being connected once.