Solving a chess puzzle where there are for some reason three black-square bishops - recognizing that the bishops are important to the puzzle is meta-knowledge.
I misunderstood your point initially, but yes I agree. In a chess puzzle that was constructed yes it is meta-knowledge. But in the course of a normal game it is not. Importantly this meta-knowledge is not strictly required in either situation.
The distinction in my mind, was that the meta-knowledge here is not about the game of chess, but about the opponent. In the case of the puzzle this is meta-knowledge that the puzzle designer gave you a hint. In the case of Nakamura's game, his meta-knowledge is information about his opponent (the chess engine) and the heuristics it uses.
Chess engines only see the board state (at least to my knowledge), while humans have some kind of information about their opponent, or the history that lead to that board state. Humans have extra information, and sometimes that information is exploitable.
Solving a chess puzzle where there are for some reason three black-square bishops - recognizing that the bishops are important to the puzzle is meta-knowledge.