I wrote the article. It was very hard to write a concise article about all of Vitamin D research, and so I didn't have space to address it, though I really appreciate the feedback. Race and Vitamin D is an interesting area. The VITAL trial, which is the largest study on Vitamin D that we have, with 25,000 participants, tried to enroll more Blacks, and in the end 20% of the participants were Black. They showed the same results, but interestingly it did seem like there might be a trend toward fewer cancers for Blacks who received Vitamin D, but this was not definitive. More research on this is needed.
The other reason I didn't get into race and Vitamin D is that we then start getting into the blood levels, and what really constitutes deficiency. I think we are a little too liberal with our diagnosis of deficiency right now.
Low Vitamin D levels of are not evenly distributed among different ethic groups. e.g. "53%–76% of non-Hispanic blacks [ had low vitamin D levels, in the Southern U.S.] compared with 8%–33% of non-Hispanic whites [0]".
Thus the risk-reward considerations of taking vitamin D are likely different for dark-skinned individuals than for light skinned individuals.
I have to assume her advice at the end is targeted at light-skinned people. As a dark-skinned person myself, I'm irritated that she couldn't bother to at least mention the above issues.
[0] https://academic.oup.com/jn/article/136/4/1126/4664238