Q: the argument that saying "this apple is similar" and "are we in a simulation" is the same since you're not clarifying what the other thing is is not valid because simulation is a noun and similar is an adjective
A: that's not the basis of the analogy. the basis of the analogy was that they both require a partner. actually, to play into your love of grammar, i might add that they both specifically seem to require a prepositional phrase, in that instance. i can also give you another example of how a noun+preposition can behave exactly the same way as adj+preposition: if you say you are "a fan of" something, or if you say you are "wild about" something. on paper, "a fan" appears to be a noun, and "wild" appears to be an adjective, and yet i think you can see that those phrases seem to occupy the exact same grammatical real estate