Carrier's definition of supernaturalism as non-reductionist explanations involving ontologically basic mental entities is something of a strawman argument and makes the term somewhat useless. (ie it is not the definition many theists would even argue)

The more typical definition of supernaturalism usually refers to events that operate outside of the normal laws of physics. This definition is potentially relevant to simulationism, because a simulator would of course be free to occasionally intervene and violate normal physical 'law' if so desired. Of course, this entity itself would still be reducible to simpler physical processes in it's own universe.