I am very familiar with the chess hustling at Washington Square Park. I went to law school at NYU Law right across the street and lived on West 3rd and MacDougal a couple of blocks away.
The hustlers would target the tourists and would never play anyone for money that they knew wasn’t a fish. It was common for the hustlers to demand a “rental fee” from the tourist if they lost. A few of them were quite good at blitz, at least master strength, and had perfected the skill of verbal abuse to throw the opponent off. I didn’t win every blitz game I played there.
One time a GM showed up (Ilya Gurevich if I remember correctly) and gave 5m to 30s odds and beat all comers.
In any case, it’s unclear what your point is about your white friend “who was one of the top 10k chess players in the US” losing to a black person. You don’t give your friend’s USCF rating. He may be able to beat you handily but he may not be actually as good as you think.
There are about 48,000 rated players in the US, of which more than 32,000 are scholastic players, and many of those are beginners with a rating under 1000. Being in the “top 10k” is unexceptional and would put your friend at Category A or above.
For comparison, I am in the 99th percentile with a rating of 2243, which may sound impressive but I would not stand much of a chance in a regular time control game against any professional IM or GM. In blitz I could probably win a few games.