That appears to be one study. The largest study carried out on penis size (without self-reporting) in the USA showed white men had the largest average by a similar margin (0.2"). IIRC, it was called the Kaiser study. I believe Kinsey was involved with it. Nevertheless, the highest university-measured sizes I've seen, globally, came from Central Africa.
Also, once again, even in the context of that study, if we accept it at face value, the point stands. The difference there is 0.1 inches length & 0.02 inches girth on average. I promise you not a woman alive could tell the difference, and it's also absurd to believe this would sustain a pronounced effect on the difference in how "tight" they are. After all, again, the average baby's head is 35cm in diameter, or ~3x what men are brining to the table.
It's so silly.