I've also experienced the limitations of making an appeals to the admissions committee based on adversity and potential and what the school could do for the student.
My sense is that the alumni interview only really affects the borderline cases or if you give a truly horrific review of the student for one reason or another.
The process selects for a certain mold of person. Diversity happens only within this smaller universe, imo.
Those are real deserving human beings having their potential limited for lack of upper crust "polish" in modern America. Institutional class discrimination is real.
It wasn't an interview in any of the usual senses of the word, really just a meet and chat kind of thing. I had no sense of being evaluated in any meaningful way. More to make sure I wasn't obviously psycho crazy and at least minimally functional, I imagine.