You seem to be conflating solipsism with epistemology. At the end of the day, regardless of whether you're dealing with a child, a bot, or a peer, you would never use the question "describe how to play chess" as a measure of understanding if the chosen entity understands how to play chess; you would just play chess with them. Such an inquiry would only probe if one understands how to explain how to play chess, which is not the same. One should expect an LLM model of being able to regurgitate a description of playing chess. One could even expect an LLM to regurgitate common strategies in chess, enough to fool some into thinking it understands what is happening amidst a posed match. Where it all falls apart is where the rubber meets the pavement. Get an LLM to teach your child chess, with no intervention. You'll learn rather quickly which one is capable of understanding, and which one isn't.