Well, incompetence in that they didn't manage to achieve clarity for all readers, but not in the sense that someone else would've been able to think of a better title that would achieve that, I think.

Indeed, you're correct. I don't know if someone put it like this intentionally or not, but looking at the number of people who jumped into the incorrect conclusion, it has the same effect as misleading headline.

Something that’s prone to misreading is misleading. Intent doesn’t factor into whether something is misleading or not and neither does when something is in some sense correct but not understood correctly by many people.

Language can be used in too many ways and not all correct ways to use it are also easily understood. Often enough that doesn’t matter because of context but here context leads actually to people coming to the wrong conclusion because the well known conflict is between some (any) kind of genetic origin of homosexuality and environmental factors being responsible.

That single mutation could affect level of some hormone during som3 crucial step of brain development and that might result in some complex behavioral changes.

It’s a scientific study so the citation is literally present in the story if you want to learn what they did:

http://dx.doi.org/10.1126/science.aat7693

Rather than making armchair dismissals, consider looking at the paper and its citations which discuss the statistical methods used. From a cursory glance, it looks like they use a standard model of how genes affect traits, which uses O(N) parameters for N genes, so the "curse of dimensionality" would not apply.