Disparate impact is orthogonal to education; it's a legal test that applies to employment, in disputes over the direct relevance of a criterion to job performance. This might affect WGU in some 2nd order way if it were claimed that credential requirements have a disparate impact (well duh, enrollment stats), but that claim would apply equally to any tertiary institution. It seems absurd, but I'm curious if that test has ever been tried against a national professional accreditation... Few quick searches didn't return anything.

The 30% profit margin sometimes also signals that there are high barriers to entry. (You already mention what I think is the big one: accreditation.)

how does racism play into this?

Sorry, talking about the history of standardized testing will get me downvoted. Guess how I know.