I don't know what de Beauvoir meant by her statement; but I think the root question is whether, aside from socially-defined gender roles, there is any essential difference between women and men. It seems obvious to me that there is.

It's biological. Sexual dimorphism promotes species survival; and dimorphism in design inherently suggests separation of function in pursuit of that goal.

Obviously, there is drift; and a social policy of denying women opportunity on the basis of sex is insupportable. But saying that there's no essential difference between women and men is ridiculous.