Prof. Munger doesn't want 4.0 GPA grad students on the grounds that a 4.0 indicates someone unwilling to step outside their comfort zones. It's an interesting heuristic for acceptance into a graduate program. Unless you're fiendishly clever and spot this blog post, most people would never figure out that they're supposed to take risks and fall short of perfection in order to open this particular door in academia.
Is that right? Is that fair? Does fair even count? Is it appropriate to have goals that we don't normally let people know that we have. I think that in certain circumstances, this sort of hidden goal setting is the only way to select for certain traits, independence of spirit for example.