I will offer some observations.
A relative, recently deceased, was president/head of a US medical school. Famous surgeon who taught at a couple of US medical schools & participated in ground breaking transplant surgery. Wrote a leading text on surgery. Lots of research articles published. Based on his background, one might think that medical research would be an important consideration for admission to the US medical school which he headed. It wasn’t. He was fairly adament when he stated that the all that his school cared about was an applicant’s GPA & MCAT score. Absolutely did not care about where one attended undergraduate school. But, this is just one medical school.
Several close friends & other family members who have attended medical school, taught at very prestigious top ranked US med schools, and also have very successful careers including in medical research are a mixed group. Some were heavy into research during their undergrad years, and some were not.
My impression is that the interview is an important factor in medical school admissions. Of course, the important question is what gets an applicant an interview.
FWIW The only close friend who was denied admittance to medical school (twice), was admitted after devoting those two intervening years to research. Went on to practice, then teaching at a very prestigious medical school, and now has a very successful practice in his specialty.
Regardless as to whether or not research leads to an interview for medical school admission, applicants must have very high GPAs & do well on the MCAT.