You are indeed misunderstanding. A game tree search is not defined by the available options for the very next move. It's about the total possible paths to the

You are indeed misunderstanding. A game tree search is not defined by the available options for the very next move. It's about the total possible paths to the end. In this case, poker is a much larger tree. Read the intro section of Darse's PhD dissertation that I linked to above and you'll understand.