Normally, for schools to give someone an II, I think the schools liked
@Julatteluver enough on paper (which is likely a mixture of stats, reference letters, ECs, personal statement, etc. I know each school is different, so I'm making some generalizations here for sake of simplicity). For mission-driven schools, perhaps they saw something in his/her/there application that aligned with their goals. So again, the applicant looks good on paper and warrants an interview.
Of the pool of interviewees,
@LizzyM has a great staircase analogy, where applicants are "ranked" based on how high or low they are on the staircase. Depending on how you do at the interviews, you might move up, down, or stay at the same spot. The school then accepts the top Xth applicants on the staircase; with the rest either on WL or rejected. So, based on that, I would say the applicant should improve on their interviewing skills (i.e. how they answer questions, how they present themselves to the interviewers etc). Again, I'm not saying that the applicant performed poorly on interviews. But, traditionally red flags (i.e. low GPA, low MCAT, bad reference letters, subpar clinic hours, etc) would likely have eliminated the applicant BEFORE the interview stage. Hope that helps and that I didn't offend the applicant in any way. Just my .02. Good luck!