Your points are spot on, but it begs the obvious question of why the NFL is conducting this test? Why wouldn't they conduct position specific tests? Why not tests that demonstrate more closely what's needed on the field?
My theory is because what they are really looking for is the freak that slipped through the cracks that they can perhaps select in the 3rd round on the cheap and has the potential to be as good as the more ready made NFL prospects. Much of what they get comes from the interviews and observing how players respond to the stress -- my uneducated guess.