The idea of the (reasonable) simulation argument is that not everything would be calculated out to the particle level all the time - the simulator would only figure that stuff out if there was some reason to. I mean, you can simulate the observable, macro-scale behavior of the sun without actually figuring out the position of every quark inside it.
But sometimes, like if some scientist is looking very close, you really do have to figure out exactly where every particle is in order to render that scientist's experience - and once you've done some of the particles, you have to store the value for the other ones too. Once they quit looking too closely, you just simulate the aggregate results. It's a tidy explanation of dual-slit type results and entanglement.
It's not, like, strong evidence or something, but it makes sense. And, while I can't think of a test, that doesn't mean a simulation hypothesis isn't testable. Under this view, these sorts of quantum effects are effectively simulation artifacts - and perhaps there's more dramatic artifacts that can be induced that would be more clear.