I think it's odd that people have conflated masculine / feminine gender roles with sexuality. I put them on orthogonal axes.
Really? I think all those things are part of nature's toolbox to cause babies to be made, which is the only thing that nature cares about. Everything else is an incidental occurence. Just because two things are orthogonal in principle doesn't mean that every possible "box" in the grid is equally likely.
In D&D terms it would be as if you had alignments, but 90% of people fell on the one diagonal between Lawful Good, and Chaotic Evil. While they're not
in principle connected, the low number of people not on the axis makes it appear they're linked.
If you are a male with "straight" orientation, then you're atracted to female-appearing people. And those people are only going to like you back if they're interested in male-appearing people. But apart from that, people are attracted to mates who have the appropriate
behavior, this is true of all species. So gender role performance is in fact part of the process of mating. And this is the entire engine that drives procreation, so there's a bias to aligning gendered behavior and sexuality in this direction.
Sure you can point to "outliers" who buck the trends, but nature doesn't care whether their are outliers, as long as there are enough "regulars" that do actually breed. One set of designs must be able to create both male and female based on a shared set of chemical signals. So of course, those signals can get crossed. Genetics is messy, so
of course nature can't guarantee a perfect result every time, it just needs to guaranteed a good enough result, enough of the time, that enough babbies get made.
And the "regulars" do the vast bulk of baby making. e.g. women who are attracted to male "provider" types and have "maternal instinct" are just naturally going to have more resources invested in their kids than ones who don't, so their kids get ahead in the game. Basically, there's a co-evolution here between the hormone signals and the gender-related traits. The process is constantly optimizing to differentiate the sexes in a way that maximizes baby making. Sure, it's not PC, but nature doesn't know or care about offending our sensibilities.