It isn't a synthetic example at all. We want two receivers of the same set of messages from the same set of senders to process them in the same order. Determinism is of utmost importance.
In your example, the vehicles' messages have no causal relationship; they are concurrent. Order does not matter. However, for the sake of determinism in a simulation, the above constraint is necessary even for concurrent messages.
In your example, the vehicles' messages have no causal relationship; they are concurrent. Order does not matter. However, for the sake of determinism in a simulation, the above constraint is necessary even for concurrent messages.