It's probably loosely based on actual medical research, but these things tend to use gender as a shorthand for other factors that tend to correlate with gender. For instance, isn't alcohol metabolism heavily influenced by body weight? And since men are on average heavier than women, they just shorten it to "women shouldn't drink as much as men". Anyway, we have a few people on here who knows about actual medicine, and I hope they are able to jump in here.