Black is also a last name, so the uppercase is not a great distinction. It's more likely about calling black people African-$DEMONYM. Black people have no problem calling themselves negros in Mexico, but this is so horrible to Americans that Mexican media has been pressured to normalize mexico-africano instead.

Edit. Actually opened the list, and it is incredibly stupid to say the least. Words like "measles", "vaccine", "solar power", "sustainability/sustainable", "elderly", "electric vehicle", etc. It's not a serious writing guide, it's a blatant propaganda tool.