Sure, if the course is very poorly designed or the student is very unmotivated, they may end up just memorizing everything while somehow avoiding understanding anything. But in real life, when someone says "Oh I understand it, just give me thirty minutes to solve it" and others "shit them out" in 5 minutes, it's usually the shitters who are ready to advance to the next level.
No it's not. I'll make it simpler. If you know the material really well but haven't memorized the problems, you will test poorly. If you memorize the problems and have no real understanding of the material, you will test well. This is obviously the opposite of what you want to test.