Ouroboros multicast conjecture

The Ouroboros multicast conjecture (apologies, but we had to give it some name) states that it's not possible to make unicast or multicast/broadcast transparent to the entity that directly engages in the unicast or multicast communication. Or similarly, it is not possible to engage in multicast and unicast with the same API.

The current formulation is rather intuitive, it would be interesting to have an adequate precise description of this (seemingly trivial) conjecture, preferably with a formal proof.

Origin

The RINA specifications have a rather interesting concept called whatevercast, which claimed to be a single API for both unicast and multicast. The observation made is that communication is n:m and unicast is just the case where n=m=1. A 'whatevercast name' which is a destination associated with __a set of rules to resolve the destination addresses__.

So, basically the proposed API is allocate(whatevercastname) and the network will resolve things for you.

Now, this 'set of rules to resolve the destination' wipes a lot under the rug.

Discussion

Why n:m multicast where n=m=1 is not unicast.