Cases will absorb impact force, so regardless of if the force is on the screen or internal components, a padded case will absorb that kinetic energy to soften the blow. That would be like saying dropping it on a pillow wouldn't be any different than dropping in on concrete in regards to the internal components. The case softens the blow and slows the deceleration the same way a pillow would (though to a lesser extent of course).
the issue is, it's to such a small extent, that it's useless. think of it this way....do you think being inside of a cardboard box is going to protect you at all from a fall from a 2nd floor window? how about just a 10ft fall? you think that box is going to soften the impact at all? no way. not. one. bit.
with the fragility of the new nexus 7, all a case is good for is keeping off scuffs and scratches....but it's soo fragile that it'll most likely break before you have to worry about scuffs or scratches. traditionally, tablets screens break before anything else in a fall....but the new nexus 7 has a huge chance of breaking from simple falls, long before the screen -- and it's not because the screen is any stronger, because it's actually quite fragile. so the internals of the new nexus 7 are literally more fragile than glass.
picture a guy jumping off a roof onto those nice soft inflated landing areas. the reason why they survive the fall is because their deceleration is slowed gradually. but tablet cases are NOT that fluffy. they don't allow for any meaningful gradual deceleration that something like a pillow or trampoline does, there's just not enough padding to 'slowly' decelerate into.
*tablet cases are more designed to spread out the force of an impact over a larger area than a smaller one.* that doesn't mean the amount of force changes, it's just redistributed.
for example, if you dropped your unprotected tablet face down on jagged rocks, each edge of those rocks will focus that force over smaller areas instead of spreading out the force evenly. think bed of nails. you can safely lay on a whole bed of them, but remove 60% of those nails from random areas, and you're eventually going to have enough weight on one point for it to penetrate, despite the same amount of weight or force. by having a flat surface covering the screen, any force against it, spreads that force out over the entire screen. but again, the nexus 7 is proven to be soo fragile, it can break internally before there's enough force to crack the screen.
since the nexus 7 was dropped flat on its back onto a flat surface, that force was spread out about as evenly as any case would have spread out that force, which means a case would have made virtually no difference. whether the screen breaks or the internals, you're still left with a brick.
cases are not designed to protect the internals of a tablet in the fall, physics just don't work that way. cases are designed to distribute force evenly and externally so you don't get too much force in one single area. they're primarily designed to protect the screen this way. but they will never be able to protect the internals until they resemble a pillow since it's impossible to redistribute force on the inside of the tablet, which is why I said they should have filled the tablets empty spaces inside with a foam, so that way force can be redistributed evenly internally.