Black and White are soulmates
yes. For me it is soulmates in a nutshell. But even that term is used so specifically that gives the impression it’s romantic.
I believe the constant focus that one should find just that ONE true relationship in stories (which comes from people to people) is the reason some people want to come up with words, like bromance, queer platonic, platonic ship, heterosexual life partners, etc.
It’s always been romance but all the pressure for people to find it, specifically young adults who haven’t figured themselves out yet and maybe aren’t interested in romance/sex, creates the need to come up with new words coz friendship in everything we consume and/or are told, is just your past time.