Google has a library of millions of scanned books from their Google Books project that started in 2004. I think we have reason to believe that there are more than a few books about effectively playing different traditional card games in there, and that an LLM trained with that dataset could generalize to understand how to play Balatro from a text description.
Nonetheless I still think it's impressive that we have LLMs that can just do this now.
If it tried to play Balatro using knowledge of, e.g., poker, it would lose badly rather than win. Have you played?
Winning in Balatro has very little to do with understanding how to play traditional poker. Yes, you do need a basic knowledge of different types of poker hands, but the strategy for succeeding in the game is almost entirely unrelated to poker strategy.