Because it changes the response. The school district changed the rules to reduce systemic racism, but two years after they changed the rules they haven’t seen a change in disparity. If the school district continues to treat this as a problem to be corrected by better rules, they won’t solve it, because individuals have discretion in what (if any) punishment students receive. Any individual’s conscious or unconscious bias will enter into the decisions. (Removing all discretion is also not a good solution, because zero tolerance policies and the like are also terrible.)
The parents want a review of which staff are giving out discrepant punishments. Even at an anonymous level, knowing whether discrepant punishment is evenly distributed across all staff, or concentrated in a few, is extremely important in figuring out how to approach the problem. Is better training and making people aware of their biases a good approach, or a complete waste of time, because most staff are fair, and much of the problem can fixed by firing a few bigots?
The parents also want more Black and Latino teachers, which would probably help, but the reasons that the district has difficulty hiring non-white teachers gets to into whole other areas of systemic racism and sexism.