This is to measure the acceptance rate gap overall, not the gap for a specific host/guest/experience. Then, after changing the product, you can measure the gap post facto and see if you actually did anything. You can't change what you can't measure.
TLDR is that that information is stripped of Airbnb identifying information, asymmetrically encrypted before perceived race is determined, then noise is added when the data is returned to Airbnb to prevent identifying individuals. This data is only used for identifying acceptance rate disparity.