It doesn't mean the check wasn't racially-motivated. If the software engineer were European, South Asian or East Asian in ethnicity (rather than African) and had the same kind of visa, would the odds of being challenged by CBP about professional capabilities in this amateur hour way have been equal? I doubt it.

Of course sometimes State indeed does get it wrong; but when CBP gets it wrong, it's not a check on that. And it's not like CBP doesn't get it wrong at least as much or more frequently than State, as with Canadian passport users and US VWP users who travel to the US without applying for a visa at a US embassy/consulate. Where is the check on CBP getting it wrong?

The game of "gotcha" and relying upon quality control checks is what results in a waste of resources and government showing its own incompetencies while fixing less than it messes up and messing up what it is supposed to fix.