I personally see it as a bit artificial and unnecessary, for a variety of reasons. For one, the "community" being adapted--in the case of a 5E Al-Qadim product--is an amalgam of Medieval and Ancient Middle Eastern cultures, folklore, legends, and myths, and just pure fantasy ideas. As far as I know, there aren't any ancient Sumerians available

. But more seriously, there probably isn't any one person, or even small group of people, that are members of all cultures involved, even if we take their contemporary correlates (not to mention, ancient Sumer and modern Iraq are only very tenuously connected).
Not to mention, if WotC held this standard, then they'd need to apply it to all products - not just non-Western. Consider all the little elements that go into, say, the North of the Forgotten Realms...how to assign a cultural consultant to that, and what would they need to be an expert of? Meaning, if ethnic representation becomes a requirement in this regard, why is an American any more qualified to write about a setting inspired by Northern European cultures than one inspired by Middle Eastern cultures?
Now if it were a book that was meant to represent a modern, real-world culture, that would be a different thing. Or if it is a very specific culture or historical period, then the relevant consult would be a good thing.
But for fantasy books that are
inspired by a variety of sources, I think the key is a combination of good research and awareness (and avoidance) of stereotypes and negative depictions. That said, I can see how having someone with relevant training in catching such things would be useful to have involved, but I don't think it has to be an Arab consultant for Al-Qadim, just as I don't think it has to be a Germanic (or whatever) consultant for the North.