Most of the people who ordered, designed, built and tested the machine are white.

They don't have to explicitly discriminate against blacks.

They can just go their business as usual, designing stuff based on their own norms and cultural habits, and it will come out as naturally discriminating.

If all those whites doing the machine's design had those "certain hairstyles" in the same ratio as blacks, and were flagged as much when they've tested it, they'd have considered this facet of the machine as useless and removed it...