When it comes specifically to Adele, I can not say that I have ever heard of it, but it would not shock me at all if it is true. The surprising thing though seeing is she is British and famous women over there have been dating black men long before she came along but then again they all got looks and comments as well. She was most likely getting those looks before she got famous and knew they would only get worse as she got more famous.
I think we can all say that without a doubt dating and being a relationship with a black man is a totally different experience from dating any other man on this planet. We tend to be the only men that women (regardless of the race of the woman) get comments looks or insinuations about. Lets be real here, you have to be a very strong woman to date and be in a relationship with a black man, because you are gonna get comments.
I know that there have been women in the entertainment/modeling fields that have said similar things about dating/preferring black men before they got famous but then things changed when they became famous. Pam Anderson before she became the biggest star in the world said that she had a serious boyfriend for years in Canada who happen to be black, Christina Aguilera was another one that was into black guys then she got famous and that ended.
Gotta remember before the Kardashians proved it to be wrong, one of the quickest ways to kill your career in entertainment was to be linked to a black man romantically.