Whoever would build the first had a limited amount of computation of Universe Minus X with subsequent simulations inside of that original copy of Almost One to One simultaneously Physical and Computational Units shrinking in computation power slightly or dramatically and irreversibly until the smallest simulation of a given universe is reached by no longer being able to emulate much.
Like the painter painting a painting of a painter painting a painting of a painter...
The ultimate reality beyond any simulation forever veiled.
Too bad that is inexorably indemonstrable and thus not scientifically immaterial ie. absurd.