Are you saying that if black people live in one society and white people live in one society, then the black one will necessarily be hundreds times worse than the white one?
Because that's what it sounds like you are saying.
That's not at all what he's saying. He's saying that, when you segment off the institutionally subjugated part of your population--the part of the population who has historically been denied economic opportunities, educational opportunities, and legal rights--you are going to have two populations that have very different growth curves.
And, historically and into the present, there are cultural incentives (racist-ass racism) and economic incentives (risk aversion) to make that happen.
Because that's what it sounds like you are saying.