Occans razor in this case applies to the complexity giving rise to a situation here though, not the complexity of a described system.
Conventional physics giving birth to our universe is currently the model with the fewest assumptions.
What would have to take place to give rise to a universe the size of a data center, running an AI model of a human? It feels like we have to bake in assumptions of stable physics, a rise of a stable system for that data center, and some path towards creating it and modelling a human.
That said, if we believe we're capable of running billions of believable simulations, then we're more likely to be in such a simulation than ground reality. But a datacenter pocket dimension bakes in a lot of assumptions that make it less likely than our own universe.