He's right, of course. I've actually had an opportunity to look at the actual "scoring sheets" used at a medical school I interviewed at. The interviewer technically broke the rules in showing me, but I did get to examine carefully how the point system works.
GPA/MCAT are overwhelmingly the most important things. While ECs count for a few points (about 10 points versus a total of 70 for GPA/MCAT, and 10 points for letters of recommendation) you could get the full 10 points by only doing SOME ECs.
Like, if you shadowed a doctor, you might get 6/10 points...having done nothing else at all. That's because about 5 different things overlapped into this 10 point category...so there's absolutely no need to shadow AND be part of student organizations AND get an EMT-B AND go on a mission trip...you'll max out your points long before that.
Sure, this score "just" gets you an interview. But, as I learned, interviews are like playing roulette in Vegas. Each interviewer asks a completely different set of questions. Some will like you from the start, some won't...it's kind of arbitrary, unless you are as charismatic and good looking as a television anchor, of course. If you had done almost no ECs, you're STILL going to be able to fill up a few minutes during the interview talking about any ECs you actually did do. Odds are, assuming you have some bare minimum level of social skills, if you get 10 interviews you are probably going to do awesome on a pair of interviews at at least one of the schools you interview at. And, if you have the grades...you will get offered 10 interviews.
The way to get into medical school for sure : 1. Have the grades and MCAT. 2. Apply Early. 3. Apply broadly, and go to all interviews offered.
Virtually anyone who does this will get in. Oh, and suck up to at least 3 professors over a semester during undergrad, and get the highest grade in their class. Also, pay a professional to edit your personal statement. But, these are minor things that anyone can do : but not anyone ends up with the necessary grades/MCATs