So-called "non binary" fashion is just that-- a fad that allows adolescents to be edgy without having to commit to surgery, much like the public declarations of homo- and bisexuality that do not reflect their actual sex habits. Heteros--especially teenage boys-- can't get off on homosex. Girls can more easily pretend because they need not have any penetration or even cunnilingus--they can play at lesbianism without a serious emotional or physical.commitment.

When I was a kid, we all insisted we were bisexual, because straightness is boring. Were we? No, of course not. We just said we were for the social clout. We'd proudly declare "I'm straight but not narrow" and then continue being as hetero as possible.

In college a lot of the girls would take it a step farther and kiss each other at parties - secretly purely as a show for the boys, of course - and declare themselves bisexual or lesbian. But by then the boys had all outgrown the need to apply trendy labels to themselves so the girls mostly stopped by junior year.

Tl;Dr every generation does this and it's 99% performative because kids are stupid