@efle -- what you describe has been going on forever, and probably will continue to do so. You understand it at the UG level, but not for med school, but it is the same. The prevalence of 520+ MCATs at top UGs is not a function of superior education delivered at the school; it is a function of a greater percentage of higher quality students attending the school as compared to an average state flagship. Also, sure, a 3.95 is harder to get at a top school, especially if the classes are curved, but so what? A 3.95 is still a 3.95, and indicates mastery of the material regardless of school attended, and the MCAT is still the great equalizer, which is why it is given such weight.
Med school adcoms use prestigious UG admissions as a screen and proxy for high quality students, just like residency directors use top med school admissions. I really don't think it's a reflection of perceived quality of the education delivered. Rather, it's a reflection of perceived quality of the candidate, by virtue of him or her making it through the prestigious school admission process.
It doesn't mean that there aren't exceptions, and that really good students don't attend all kinds of UGs or med schools. It's just that top schools are "name brand," and just like soap or cereal, name brand students are deemed to be better than generic, even if in reality they are sometimes exactly the same, or on occasion, the generic being higher quality!