That isn't randomness. That is the applicant being a more borderline applicant than they realize. They may have no idea that they were borderline. And more importantly, they don't know why they were borderline, but they were. People get very caught up in the numbers because it is the easiest thing for them to sink their teeth into, but the reality is that other parts of the application can play a significant role. Students are notoriously poor evaluaters of their own application and honestly, unless you have read a couple hundred (or thousands) of applications, I doubt that anyone is really able to discuss the relative weaknesses of an application. I've lost count of the number of letters of rec that I've been told were "strong" that are mediocre at best. Personal statements? Forget it. Everyone thinks that it their is strong, or at least good, mainly because they don't have types... Then there are the interviews. Lord have mercy...
In general, medical school admissions does a poor job of selecting for desirable physician qualities, it is very good at finding people who will survive the schooling/training because it selects for academic prowess over all else, but it isn't great at the other things. But, when I hear about or see an application of someone with reasonable/strong scores that didn't get into medical school, or going down further on their list than they were expecting, there has always been a good explanation. Maybe not on the surface, but as always, the devil is in the details.