I think this is generally true, although in a gay family setting you may not get a good role model for the opposite sex in that role.
Here is the thought experiment, heterosexual girl raised by two women, marries a young man, who behaves badly in the relationship. Now it is clear that one should never tolerate abuse in a relationship but people do all the time, and they make excuses for it if they are emotionally compromised. So what prevents our heroine from not rationalizing "oh this is normal for men in the role of husband." ? That would be the wrong conclusion but they may not have an intimate (or internal) model of a good hetrosexual relationship. It works the other way as well of course, gay children raised by heterosexual parents not having a role model for a well functioning gay marriage.
I don't know if that is a "big" problem or just an existing flavor of the "kids in a good/bad family environment" knowledge. But as the article points out, we're still about 10 years away from the first wave "second generation" kids from gay parents reaching a sizable enough cohort to make any useful observations.
Of course your last point suggests the question, "What sort of city would twins raised by gay wolves found?" :-)