Models like the holographic principle can be tested both mathematically and through experiment. Full tests are beyond our current capabilities but not unfalsifiable in theory.
This is like writing code to run a VM to detect if your code is being run inside a VM.
If the answer is no or yes it doesn't really say anything about whether the parent machine is running a VM with your code inside.
The results of the experiment wouldn't say anything about the simulation hypothesis.
The simulation hypothesis follows a similar logic with one less data point. Knowing that experienced reality could in theory be nested inside a superstructure but not knowing the actual deployment of such nested experiences, we would guess that our experienced laws of physics probably exist inside a superstructure.
What the properties of that superstructure are beyond the hypothesis itself because we don’t have the same knowledge of virtualization of physics as we do of OSs.
String theory is one attempt to describe that structure based on mathematical reasoning. The simulation hypothesis just states that physics is likely to be virtualized inside another system and that it’s worth exploring physics at its limits to understand the properties of that virtualization.
It’s falsifiable through the development of analytical methods that don’t fully exist yet but not theoretically unfalsifiable.
