So you are suggesting that there are providers that get off fucking white dudes, asian dudes, indians, hispanics, american indians, Polynesians, and middle eastern dudes, AND all of those dudes can be any combination of fat, old, or ugly, but she just can't get an orgasm from a black dude? And therefore, they prefer not to book with them?
If you are searching for a reason not to attribute racism or the thoughtful application of stereotypes to the provider, then I would expect her ad to be much more restrictive. Like limits on age (and not that you have to be OVER 40, but rather under 40) or weight as well. For example: no AA men, no Indian men, no middle eastern men, no fat men, no bald or balding men, no men over 45, and no ugly men (please attach full body nude selfie). That I would buy, she's looking for a type; but just no AA men . . . nah, that probably isn't a he doesn't turn me on rule.
BTW, you need to see an Asian girl, they are awesome. Get focused and fuck one! Philippinas are phenomenal too! I haven't seen K-girls, but when I find one that has a more open menu I would be interested.
And you should see an AA provider, one with an amazing ass