The gender and racial identities of underrepresented populations is relevant to a whole host of readers, including researchers, educators, social scientists, etc. But beyond that, it's also relevant because the article references Black History Month and is even tagged with a "Black History Month" tag.

As far as why he is considered black, it's probably because someone found it economically advantageous to consider one or more of his ancestors black at some point in their history, and the norm was that a son of a slave was also a slave (i.e. "black"), regardless of complexion.

Relevant: https://psmag.com/why-your-race-isn-t-genetic-559908897f93#....