Quick point to consider here:

The same-sex parents in these studies are, I’m thinking, probably almost all adoptive parents.
And, because adoptive parents have to:
A: be fairly well off, or at least very stable, financially.
B: pass rigorous background checks and meet other qualifications.

Point being, adoptive parents tend to be the “cream of the crop” so to speak.

Whereas biological parents could include everybody from a very emotionally stable, healthy, well-educated married couple to a pair of shacked-up meth freaks living in a van down by the river, it stands to reason that at first blush, the scale will tip in favor of the adoptive (gay) parents to begin with, esp. with small sample sizes.

As to this whole notion that “both a mother and father don’t matter,” hmmmmm… I have to be more than a little dubious about that. Hell, just type “the importance of having an involved father” into Google… and you’ll get a gaggle of hits --- many of them from exhaustive studies by a wide range of experts.

To just give one example, I think it’s been shown over and again that a girl’s relationship with her father, esp. during her teenage years, will set the pattern for her relationship with men for the rest of her life. Too often, an absent, or cold, distant father, will lead to a young woman who sluts herself out just to get attention from men, and/or constantly ends up in abusive relationships.

So, to just say, “oh, it makes no damn difference at all whether kids have both a Mom and Dad” is, IMO, utterly insane.

That’s not to say a gay couple can’t raise a healthy child. But I think it’s a good alternative model, not a substitute for the real thing.