Hi OP. I watched some of this yesterday and have been reserving comment.
My thoughts with the caveat that I only got through the first 20 minutes:
I think she highlights the issues with growing up mixed race well. I do take issue with her saying black people don't want to hear about mixed race issues. I think black people, women in particular take issue with mixed race people using their experience as a mixed race person to downplay or dismiss racism "because it never happened to me", black people must be lying/playing the victims etc., while refusing to acknowledge they have privilege and society will not treat them as an unambiguously black person.
I would never tell anyone how to identify themselves, but I do think mixed race is a separate identity different from being black and it is okay to acknowledge that, they are those who see themselves as black and others who see themselves as mixed race/biracial or even identifying more with white people which is all okay, because it is their lived experience.
Because being black is the only racial identity a black person has, they can't walk into or choose to be mixed race, no they are black, but when you can walk between spaces it is up to you to be respectful of the space you are entering and the inclusivity of the black community.
Even Zendaya said “I am Hollywood’s, I guess you could say, acceptable version of a black girl and that has to change.”
and
“I feel a responsibility to be a voice for the beautiful shades my people come in. Unfortunately, I have a bit of a privilege compared to my darker sisters and brothers,” she said. ” ... Can I honestly say that I’ve had to face the same racism and struggles as a woman with darker skin? No, I cannot. I have not walked in her shoes and that is unfair of me to say. But I’m completely behind that woman. I want to be a part of the movement and growth. And if I get put in a position because of the color of my skin where people will listen to me, then I should use that privilege the right way.”
I think that is why people may point out that your views are not wholly representative as a mixed race person if you assume your experience is that of other black people and they just haven't worked hard enough, not that black people withdraw and put their support on mixed race people based on "how cool they are". Having parents and grandparents who have at various different times lived under the apartheid system, I have mixed race family members who take offence at being called black because of the racial system that existed under that government and the negative connotations they associate with being black. So I have always subscribed to the belief, that mixed race people identify themselves as I take that cue. MM considers herself biracial so that is what I will call her not black, whereas Zendaya and Obama consider themselves black so that is what I call them.
I didn't get to the quotes you mentioned but I would find them offensive.