I'm all for handwritten tests, but it's more complicated than that. If you're actually writing for 2hr+ and haven't studied appropriate technique or bought some sort of crutch like a pencil holder then the repetitive motion will absolutely cause cramps for a fraction of the class regardless of being 20ish and healthy, and they might not find that out until they're forced to write for 2hr. The muscles manipulating a pencil (with poor technique) are much smaller than those manipulating a post hole digger, so that comparison isn't fair.