Jonathan G Cannon - that's exactly right. I think the term "simulation" is just a good starting point, not necessarily the best way to conceptualize what's going on. Similarly, thinking of God as "posthuman" may introduce all kinds of concepts that aren't really applicable.
Many of the popular level discussions of the Simulation Argument have imagined our creators as being "teen gamers", or something similar, immature entities in possession of disproportionately massive tools.
But all evidence from our universe indicates that this existence is huge, consistent, and thorough. Our creator(s) are likely beings massively more complex than the universe we perceive.
And at that scale, any concept of "artificiality" dissolves into the stretches of existence we're really dealing with.