and its existence cannot be relied upon to substantiate anything else
the hypothesis wouldn't present itself at all without hearsay, or just be invalidated by all experiments and useless for building upon, compared to just using the substantiated resources at hand: in your analogy that would be all of the other RAM and computational resources to your benefit.
whereas if you play hide and seek with a friend that says theyre going to hide in a magical land you cant access, then you cant play with that friend anymore and thats the totality of the observation, compared to the friend thats ultimately just another process hiding in RAM.
Also, if the being is super intelligent and running us in a simulation, can you really subject it to experiment?
That would be like processes running in a container going rogue and demanding evidence of their host environment.