I never buy the argument that coaches with success at lower levels are among the best at their craft and would automatically succeed at the higher level. Not that some could not, but I don't think it is automatic.
The coach at the lower level often have superior advantages over the competition, such as a more established program, more consistent influx of talent, and better funding than their relative competition.
Look at Fran dunphy, for example. Was a consistent winner at Penn, then stepped up to a higher level and has not performed as well as expected. Well, at Penn, he coached at a program that was more established, better funded, and had a more consistent influx of talent than their relative peers. Now coaches deserve credit for getting to that point, but it wasn't like Fran was some great in game coach at Penn, he just enjoyed institutional advantages over his peer competition. Fran has shown while at temple that he is a very average coach.
Same might be true about this Mcgee guy. Just because he is a good high school coach doesn't mean he would have what it takes to win at the college level.