In my experience these rules are either so restrictive they only apply to a very very few white men (like hard sf which only uses cutting edge accurate hard science well enough to impress someone with the relevant degree. The only authors I can think of from the last decade or so are white men..but there's two of them) or they apply mostly to white men and then people apply them inconsistently eg Apparently I Write Like a Girl.

But yes, even when it's not applied inconsistently "normal" does "happen" to end up mostly describing white male etc books, and getting people to question their assumptions is incredibly difficult.