But isn't grammar is ultimately an appeal to an imposed hierarchy/power structure - who says/controls what's "correct"? Answer: those who "know" i.e. those who have been taught the rules and have accepted them as valid and as something to police.
In this context, couldn't we just take this to mean `native speakers'? Depends what we mean by ``grammar'' I guess ... Anyway I don't know that, at least on this reading, we should understand the rules as `something to police,' but more like `something we intuitively already know.' Surely we wouldn't try to quote/paraphrase someone's speech by saying `He there is a problem that said,' for instance. Old news to everyone here?