I didn’t say that it’s not possible, I said a good pre-med adviser will be able to help the student plan.
Some med schools won’t accept required courses from just any school so I agree, it’s a case by case basis. There may be certain study abroad programs that offer courses that will work for med schools. There are programs that will allow for extra curricular medical work, volunteering, shadowing, etc. while away.
Some students don’t apply to med school until senior year so have more time to get all the required courses done than those who apply at the end of junior year. Amherst, mentioned in OP, really prefers students apply senior year, for various reasons.