Damage taken by wuxia characters

It seems that heros like XF can take and dish out palms with the force of tons behind it, but only when its something like a fist or palm or kick with that much force behind it. If a 2 ton rock were to hit them, even if they were ready for it(but not allowed to block or deflect it), they'd probably get seriously injured. Why is this? Does inner strength only blocked other inner strength attacks? And does this count if someone throws a rock instead of directly hits them? If this is the case, wouldn't it be smart, no matter how high your martial arts, to carry some sort of weapon to be able to hurt an opponent? It'd be silly to rely on your palm and fist skills when they can be neutralized completely by someone with comparable strength, when carrying something like a little hammer even is enough to seriously injure them if you hit them with it instead of your palm.

In physics terms, we first need to define what does having a 2000lb punch palm mean? A 2000lb rock only does damage when it is moving, we can derive a momentum and KE for the rock based on its mass and velocity. Does a 2000lb punch equal a 2000lb mass moving at 1m/sec? 1ft/sec? Or something else?

Alright let's use a 100 pound dense rock then, that is about the size of a palm in terms of surface area that will hit your opponent. I haven't taken physics for like 6 years so I don't remember anything, but I'm guessing a rock of that size thrown at somebody would not cause more than a couple thousand pounds of force, something that wuxia characters can accomplish with their palms. However I imagine someone getting hit by that rock to be seriously hurt, while the force of the palm seems to be absorbable.

the inner power is easier to defend if you have superior inner power. equal inner power and you suffer damage. it's the same as if you were hit by a rock. the rock is like being hit with a weapon. weapons hurt with even any inner power. the monk who hit ZSF was using an external technique with weaker inner power. ZSF suffered mainly external injury but his inner power protected him from serious internal injury.