The idea is that to be outside the universe is to be causally disconnected from it, not to be outside of some arbitrary system. A "universe" is not an arbitrary system -- it is the whole of reality.

A computer program is not a universe independent of the programmer. They both exist in the same universe because they are causally connected. If they were in different universes, they must be causally disconnected. You're whole argument rests on the assumption that the program and the programmer reside in different universes, which is clearly not the case.