It’s the “pipeline problem”—by the time an employee enters the workforce, their skillset is the product of everything that came upstream (education, family circumstances, living conditions, etc.) If someone spent their childhood living in poverty (malnourished, inhaling pollution, in a house filled with lead paint, attending poor schools, etc.), by the time they enter the workforce, the resulting deficiency in cognitive achievement will be dramatic and unsurmountable relative to someone who spent their childhood sans toxins, well-fed, and attending good schools.

Suppose systematic discrimination against certain ethnic groups “X” has made them disproportionately more likely to grow up in poverty, which (along with many other systemic factors) causes a huge cognitive deficit relative to other ethnic groups “Y” who have not experienced systematic discrimination. Some jobs’ skillsets are predicated on cognitive ability, so ethnic groups X will be disproportionately underqualified (and thus underrrepresented) in those jobs relative to ethnic groups Y.

Many DEI initiatives prescribe that the ethnic makeup of a company/institution ought to perfectly reflect overall population demographics. This will, by definition, necessitate lowering hiring standards for ethnic groups X, since a much smaller proportion of them have the necessarily skillset relative to their peers in ethnic groups Y, who haven’t experienced systematic discrimination.

No, I just made it up (sarcasm). Jokes aside, these are just my observations. While writing my comment, I tried to look for online sources backing up or disproving what I said, but I haven't found much.

I think this is just an area which is not really written about.