This article could have been written to not push people's buttons so much, but you've got to admit: there's a significant difference between "weeder" classes and later classes that actually focus on understanding.

Calculus courses are the worst offender I can think of. They're not about imparting you with a complete understanding of the relevant mathematics, but much more about whether you can stomach being made to memorize lots of pattern-matching heuristics to do endless reams of tedious problems. Contrast this with an upper division or graduate course: they're much more focused on concepts, patterns, and understanding. The curriculum even admits this; they have the "advanced calculus" upper-division courses for actually teaching the underlying math.