I'm not sure why you find this so hard to believe or why they would need to touch your property in a scenario where they are replacing or repairing a part other than your property. Apple itself has certain user replaceable components in certain products, but there are limitations. Other companies are less stringent with those limitations.
Either way, Apple is completely justified in taking the stance they have taken with regards to warranty repair and with regards to this specific situation. I'm not so sure a Dell tech would repair a battery in a PC that showed signs of water damage.
The minute someone else opens my computer case, they are liable for any damage that might occur. They might not touch the components. But if I get the system back and it is broken, who is to blame?