Is it though? If humans instantly realise that the three black bishops have some special significance and a chess engine does not then apparently the chess engine lacks some understanding that humans do have.
If, for instance, the name of a chess problem includes the solution in it, written in plain English, no current chess engine is going to pick up on this bit of 'meta' information - yet any English-speaking human trying to solve the problem would be trivially able to use it.
Does that make humans 'better' at chess than chess engines? Not really. Does it make humans 'better' at solving a given chess position, given some metacontextual clues? It does, but it is a bit contrived.
If an AI can't pick up on it then that suggests it lacks parts of what to humans would be a basic understanding of chess.
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.
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.
If we’re just going to say, “no one will ever do that in real life” then the humans will just start finding AI weaknesses and how to maximally exploit them.
I play board games and I definitely “play my opponent”.