this is a larger cultural issue. lots of african americans expect to have families that look like tv families where their kids look like the mom was creeping on the side. when the kids don't come out that way parents behave passive aggressive towards the child berating them for being nappy headed and/or dark ("boy if u don't get ur nappy headed black ass in here")
with LGBT they don't have kids like heteros do, so they have to be more honest about the type of kid they want whereas with hetero couples a Bill and a Claire will just hope to get a Sondra and be let down they had a Vanessa (they'll still love her and be happy to have a child). so i don't think this is about sexual orientation
however i may be mistaken and these ladies in the stories just wanted to raise a multiracial person because they enjoyed the idea of a person experiencing and belonging to multiple cultures.