I think they are basically saying he acts white due to his mannerisms ie; personality, intestrests, vernacular, they are associating it with whiteness. There is a term for this in different cultures as well, in the black community its "oreo". Like I used to get called "white girl" because I spoke proper and liked rock music growing up. They are basically associating intelligence, certain hobbies, and manners with race. As if POC's can't have those same personalities,interests, proper vernacular language exist within their culture. There's no way to sound "white" There's no such thing a "white music", speaking proper english isn't "white" thing. It's rooted in white Supremacy, and internalized racism. Sorry for the long reply.