Where is your evidence that "a 3.25 GPA from XYZ college, is more impressive than person Q who got 3.75 from ABC college"?
As we all know now from Moneyball, long-held views can be wildly ungrounded in reality, so why should I believe "those who have interviewed several years worth of interns and entry-level hires" are any better at judging competence than, say, professional baseball scouts in the pre-Moneyball era choosing someone based on how sexy his girlfriend looked?
Or any better than orchestras before the introduction of blind auditions in the 1970s/1980s. Before then, female musicians were 5% of the top orchestras. By 1997 (see 'Orchestrating Impartiality: The Impact of "Blind" Auditions on Female Musicians') they were 25%.
Or any better than the hiring practices where the only difference in a resume was a "white" name vs. a "black" name. The resumes with a black name required more attempts to get a callback (see http://www.nber.org/digest/sep03/w9873.html )
Unfounded unconscious bias pervades everything. Why should I assume that there's no unfounded bias in your observation, given that all attempts at quantifying what you believe to be true have failed to find a long-term predictor of success?
Also, there are plenty of jobs where one doesn't need to know much about the underlying science in order to be successful. Programming is not unique in that regard. One can be an excellent chef without knowing "rigorous" food chemistry, an excellent athlete without a degree in sports medicine or biology, an excellent writer without a degree in English, an excellent musician without knowing much about pressure waves, an excellent CEO without a business degree or training in economics.