You're correct that the theoretically optimal play is entirely statistical. Cepheus provides an approximate solution for Heads Up Limit, whereas these LLMs are

You're correct that the theoretically optimal play is entirely statistical. Cepheus provides an approximate solution for Heads Up Limit, whereas these LLMs are playing full ring (ie 9 players in the same game, not two) and No Limit (ie you can pick whatever raise size you like within certain bounds instead of a fixed raise sizing) but the ideas are the same, just full ring with no limit is a much more complicated game and the LLMs are much worse at it.