Then that assumption is outdated, which is fine as long as, now knowing that, it is appropriately adjusted.
You can sorta refer to white people in that way but it doesn’t really have the same effect because of things like power dynamics and the fact that we are able to know where we’re from quite easily. For Black people it’s a cultural identity they needed to build nearly from the ground up, for white people it really is just a way to talk about a group of people based on their skin colour and generalized stereotypes. No one is White because they have connections to their more specific history, but many people are Black precisely because they don’t.
White but black would just be choosing to capitalize White for all the reasons it’s less deserving of it yet admitting those things can be valid so yea, 100% sketchy.
I’m not against “Black and White” and “black” is still a valid thing(some guy from Zimbabwe moving elsewhere can be African-American or African-Canadian, for example) but I’m also pretty ok with “Black and white” as well, especially in places where even white immigrants are treated so differently to citizens of colour. Look at how Musk is, on paper, a prime example of an immigrant who really ought to be deported from the US but is, despite being 100% African, treated with all the privilege his skin colour affords him there.