I'm going to wager an uneducated guess. Black people are less likely to go to the doctor for both economic and historical reasons so images from them are going to be underrepresented. So in some way I guess you could say that yes, latent racism caused people to go to the doctor less which made them appear less in the data.
Where the data comes from also matters. Data is collected based on what's available to the researcher. Data from a particular city or time period may have a very different distribution than the general population.
