I would imagine it's not a joke. His comment is factual if you interpret "women" and "men" as a population and in context of chess performance(not in general).

> Please respond to the strongest plausible interpretation of what someone says, not a weaker one that's easier to criticize. Assume good faith.

it's true of the best chess players, and in a couple esports I know of, despite women having no innate disadvantage. doesn't stop my mom from beating me every time we play.