Knowing stuff is important, but knowing stuff is distinct from rote learning. I know that 6x8=48, but that knowledge does not hinge only on repetition and reinforcement -- it's cached in my memory for quick access, if you will, but I can still have the understanding that backs it up. In the same way, I know that the derivative of x^2 is 2x, and I memorised this without rote learning it. That's inevitable.
On the other hand, memorising an essay word-for-word circumvents that whole aspect of understanding, so you haven't actually learnt anything, and no new knowledge has been gained. Similarly for memorising formulae.