My DD22 will also be applying to UW. I read the essay prompt you’re referring to differently. In my opinion it’s asking about the student’s community or family, how that has impacted the student and how that background will add to the diversity of UW.
I agree that talking about his jazz family or community and how he will share that background at UW will be a much more impactful essay. It does not have to be about race and in this case, it probably shouldn’t be.