How is that relevant in any way?
What if they were all poor and white, because the study creators didn’t care about poor people, but also were concerned about the clarity of the data for actually improving health for White people, viewing any possible variation introduced by a more representative study population as noise?
(Asking because that is, in fact, how the study was designed; at least, the targeting, the assumption about why it was targeted that way is an inference.)
https://nsarchive2.gwu.edu/radiation/dir/mstreet/commeet/pm0...
This is likely true of the radiation experiments, but is not indicated in the article.
It's not, in fact, quite the opposite is true: the subjects were all white, by express design.