I've never heard a non-hierarchical simulation hypothesis.

Consider an agent that has to simulate itself in order to understand consequences of its own decisions. Of course, there's bound to be some logical uncertainty in this process, but the agent could have exact definition of itself, and so eventually ability to see all the facts. For two agents, that's a form of acausal communication (perception). (This is meaningless only in the same sense as ordinary simulation hypothesis is meaningless.)