Great video, I like these guys. It's not true, however, that there are no games that explore themes of motherhood: the author of
this article makes a good argument for why Super Metroid explores themes of motherhood and puts the player in the role of a mother figure. He over-analyzes some aspects of the game, I think, but he makes a pretty convincing case in other areas. There are also links to several other good articles about femininity in games.
This is another article on the subject of feminism and games that I found particularly intriguing; it argues that Bayonetta is actually a feminist game because it demonstrates that women don't
have to reject gendered stereotypes to be strong, independent characters--in fact, there can be something empowering about using gender roles to transcend the boundaries imposed by those roles. This is kind of along the same lines as the discussion in the video of the way in which normal human beings often accept some gender roles while rejecting others, and often the interaction between the two is what makes for interesting characters.