[nimih]

I think you're being profoundly uncharitable in that characterization of the author's work here, in that if you read the paper (and, really, even just the abstract), you'll see that they clearly understand the existence of such possibilities, and have simply chosen to limit their investigation to what their area of professional expertise (namely, the physical sciences) can assess with confidence. An illustrative quote from the concluding discussion:

Guessing how conservation laws for energy and information applies in a universe with entirely different laws, or whether they should even apply in the first place, appears impossible and this entirely prevents us from guessing whether the SH is possible in such case. For example, hypothetical conscious creatures in the famous Pac-Man video game in the ’80s will just be incapable of figuring out the constraints on the universe in which their reality is being simulated, even based on all the information they can gather around them. They would not guess the existence of gravity, for example, they would probably measure energy costs in ”Power Pellets”, and they would not conceive the existence of a third dimension, or of an expanding space time, and so on. Even if they could ever realise the level of graininess of their reality, and make the correct hypothesis of being living in a simulation, they would never guess how the real universe (”our” Universe, if it is real indeed) function in a physical sense. In this respect, our modelling shows that the SH can be reasonably well tested only with respect to universes which are at least playing according to the Physics play book - while everything else appears beyond the bounds of falsifiability and even theoretical speculation.