I've got a nonbinary friend who presents somewhat feminine, and they always say that anyone who finds them attractive is gay by default. So I guess what I'm saying is I'm not totally straight
They're using the (Greek-derived) scientific definition of "hetero" (i.e. different) vs "homo" (i.e. same). By those definitions, any cisgender + non-binary pairing would technically be heterosexual.
Yeah I define myself as heterosexual cos I'm not attracted to people of the same gender as me. I'm not non-binary so being attracted to/sleeping with an enby person is not gay, at least according to how I define my own sexuality.