Any picture of her face, on any campaign poster in any of her campaigns, shows her Black heritage. She doesn’t have to say anything about it, it’s obvious. And Harris is a common Black name. Her Asian heritage is not as apparent, so it bears mentioning. I might also mention that the Asian and Black communities have a history of discomfort with each other, so being obviously Black could have caused some Asian people who didn’t know her full heritage to vote for the white male Republican rather than a Black person. Black people have more experience with mixed-race heritage. Being a savvy politician, knowing how to approach different people, is a positive thing.
But she’s always run on her own capability. It’s others who tout or disparage her racial experience.