I can verify. My youngest daughter worked in a restaurant in Oklahoma while she was in nursing school. The minimum wage for ‘tipped’ workers was $3.63. Not one Black ever tipped her more than 5%.
She’s lucky she got any tip. Here in New York they NEVER tip, and if they do it’s usually like a penny or a nickel.
Blacks not tipping and/or not tipping at all goes back decades. From when I served while in school (was averaging 17-19%, when 10% was norm) and receiving little appreciation from black patrons. And family members in the past two decades have told of the demands/complaints of black patrons, the mess left, unruly children, extremely loud conversations disturbing entire rooms and the resultant poor/no tip left.Of course the race card is sometimes played. Far too many generations from the 70s, 80s, 90s have been handed the urban legends that continues to result in the never ceasing proverbial 'chip on the shoulder'.
Been told that many of the black staff also tell the various seating hostesses not to seat black patrons at their stations. As their experiences conditions one to avoid pain, insults, hassle, extra work for little appreciation.