Some interviewers might take a dim view of people who claim to be something they are not and they will push and push to see if you are genuine or a fraud. If you got your interview in part because of your grit in overcoming real hardship, then it shouldn't matter with regard to the outcome if you were questioned about that or your opinion of some health care policy question in the news. If the person who wanted to be assured that you were genuinely of low SES growing up, and your answers provided that assurance, then you're golden.
I'm rather surprised at the interviewer's questions as I can see in the AMCAS application how an applicant paid for school (% need based scholarships, % merit based scholarships, % family contribution, etc), whether one worked before age 18, and (optional) parents' occupation. But maybe the school that interviewed you doesn't make those sections available to the interviewer and the interviewer was just going by something in an essay.
If the questions were related to material in your application, and not protected (age, race, sex, gender, gender-expression, religion, military service, child-care, etc, etc) then it is fair game in an interview.