I don't have to try and imagine how Magnus Carlsen understands chess, since I also understand chess, and I operate with the assumption that other people are not zombies and possess a similar form of consciousness. My comment works regardless of the skill of the player.

Imagine you have never played chess, you have no concept of the rules or how the game is played, yet you've learned the entirety of Stockfish's algorithms and can dutifully run them step by step on a piece of paper when you look at a chess position. You would be the strongest chess player ever, and yet you would have less understanding of the game than even a beginner. Just because you can take an input and produce an intelligent output does not mean there is any sort of underlying understanding. This is really just a modification of Searle's Chinese Room Argument, and one of the most famous refutations of functionalism.

https://plato.stanford.edu/entries/chinese-room/