This is an example of "the settings problem". When a system has even a moderate number of behaviors controlled by their respective settings the number of possible interactions rises exponentially. Combine that with different possible user behaviors and you get a combinatorial explosion of possibilities with some weird results that are non-obvious even to experts.
That's a good point, plus it's not just (states x transitions), it's also a whole bunch of hidden state: the other guy's state as well as all the packets in flight.
