I'd always be slightly wary of any study saying anything definite about family life because I do think it's far too much of a personal thing. In particular even if there is a general trend that, say, this particular practice benefits children, it might be that in one specific case it turns out to be anything but helpful.
As an example, in general two-parent families are better than one-parent families, but particularly attentive single parents are just as capable of bringing up healthy, happy, well-rounded children as other families. So the sweeping statement risks missing a whole lot of subtlety.
I expect a similar thing to be true here. Even if, as has been claimed earlier, there is some apparent correlation between improved health and having same-sex parents, I highly doubt that this is specifically due to the genders of the parents. A far more likely idea might be that, given it's necessary for same-sex couples to specifically plan to adopt/ go through some lengthy paperwork process to allow for Artificial Insemination or some such, that the children will therefore be most definitely wanted. The same is true, of course, of the vast majority of two-parent families, but the statistics might just be skewed somewhat by various unplanned children, or children who were planned but born to parents who never had to go through a vetting process that might have shown them to be unsuitable parents or the like.
In the end, the best thing for children is to be brought up in a loving, caring environment. There is every reason to believe that same-sex couples are equally capable of providing this, and it's therefore a shame that the DM headline puts the emphasis on "Lesbians" as if somehow this would be a particularly bad thing.