In a predominantly white society, it is perfectly conceivable that you'll hire predominantly white people even if you are completely unbiased, purely because they are strongly over-represented in the population. White people hiring white people is thus not a statistical outlier, and while there is definitely nepotism going on in this cadre as well, it's less easy to pinpoint just based on the race.
On the other hand, you will likely have to go out of your way to build a team mostly staffed by minorities unless there's some other bias, e.g. that minority is over-represented in your specialty. In this case, if you have a team purely of a homogenous race that is otherwise a small minority of the overall population, it is more of an outlier. That's not saying there's nepotism at hand, but the likelihood of such a team composition arising naturally without some direct bias is simply lower than in case of a team composed of the major race of the population.