Would that be enough to prove it? If the LLM was trained only on a set of legal moves, isn't it possible that it functionally learned how each piece is allowed

Would that be enough to prove it? If the LLM was trained only on a set of legal moves, isn't it possible that it functionally learned how each piece is allowed to move without learning how to actually reason about it? Said differently in case I phrased that poorly - couldn't the LLM still learn the it only ever saw bishops move diagonally and therefore only considering those moves without actually reasoning through the concept of legal and illegal moves?