The probabilistic argument can be made the other way:

All the information for a simulated universe needs to be stored in some form in the outer universe, but the outer universe would also contain information not used for simulation.

If we consider an arbitrary piece of information, chances are it exists in the outer universe only - unless more than 50% of the outer universe is used for simulations.

If 100% of the outer universe is used for simulations, than the simulations are the outer universe(s).