Emphasizing the race that will get more votes... They know that Blacks are not too keen on voting for Harris, so they bring out her blackness by making her a black person.

2016: AP
"California's Kamala Harris becomes first Indian-American as Senator"2020: AP
"Biden pick Kamala Harris as running mate, first Black Woman"Fact checked True about the headline... However, it is also true that Harris is mixed with Jamaican and Indian blood. Her father is Jamaican and her mother is Indian (not native American).
But, the main issue... the outright pandering for votes from the different race at different time. Kinda like how Obama was portrayed - as a black man, nothing about his 'white' side is mentioned at all... same with Tiger Woods, nothing about his Thai side is mentioned.