No one gives a crap about the MCAT once you get in and you might get stuffed in a locker if you bring it up. After all, med school is exactly like middle school.
And similarly, once you match, no ones gives a crap about your Step scores. Your test scores never mean as much to the people evaluating you as you think they do.
And as far as the study referenced above goes, big surprise that the AAMC came out with a study supporting a test you pay them to take. It is probably a better predictor of Step success (than undergrad GPA) because they're both uniform, standardized tests written by arms of the similar/associated organizations--so with the same amount of prep for both tests, your scores should be similar. Also, that study is from the early 90's, and I am sure that the content of both the MCAT and Steps I/II/III has evolved in the last 16 years. Additionally, it is a fact that Step I scores, especially those at the higher end of the spectrum, have been increasing steadily in recent years--to the point where some members of the AAMC have suggested replacing the Steps (with another test that would somehow be different)--how do I know that MCAT scores retain the same predictive value they had in 1993?
Having finished med school, I am aware that statistical trends are slightly less than written laws of prophecy. However, I've heard a lot more stories like "I had ~30 on the MCAT and destroyed the boards" than the other way around. Maybe it's because people have to actually learn to study in med school or they care more about the Steps so the prep is better, or learning methods get refined, I don't know.
But one thing is for sure. The MCAT is fat and dumb and you should forget about it the second you are accepted to medical school. Man, I hated that damn test...