I think these stories exist because they sit at the intersection of two powerful story patterns, Fish Out of Water and Protagonist As Savior

Yeah, there is that, except there are so few Fish Out of Water who are POC navigating white culture (unless I'm ignoring a lot?) and very few protagonists of color too =(. Sigh. Or else you would have the Black Savior trope... but we don't, we have the Magical Negro, because he helps the white character along with the white character's question, as opposed to having a quest of his own.