Are you suggesting that we use an LLM as an interface between the AI and the player?

Why would anyone choose to awkwardly play using natural language rather than a reliable, fast and intuitive UI?

No, I think they're suggesting the LLM should literally be "talking shit", e.g. in a chat window alongside the game UI, as if you're in a live chat with another player. As in, use the LLM for processing language, and the chess engine for playing chess.

I think this is quite an amusing idea, as the LLM would see the moves the chess engine made and comment along the lines of "wow, I didn't see that one coming!" very Roger Sperry.