It's a mix of both. What emphasis is given to stats vs interview depends on the school, but they both absolutely do matter.
The schools that I've seen either score you (points for GPA, points for MCAT, points for interview) or vote on you (like 3-30 people vote yay or nay on your admission). If you fall in a range of points or votes, you get accepted. Below that, you get waitlisted or on hold. And if you get below a certain threshold, you get rejected.
It could be a mix of things that you are on a waitlist. If it's your GPA, you can't do much at this point. However, if its your interviewing skills, you can practice in case of future interviews. It also helps to send an update letter in a little while so that they know you're interested. DO schools care about interest.