You may ask, how does the third party verify if the buyer is lying when he requests a refund? Dead and simple, all delivery companies have a auto-tracking system, which will update the escrower about the status of the package, once the buyer signs the package(which is required if he wants to accept it), the escrower will be immediately informed, there will be no way for you to lie.
This is already how the chargeback system works. When the buyer initiates a chargeback, the credit card company asks the merchant to produce a "proof of delivery" signature. If the buyer signed for the product then the merchant doesn't have to eat the loss. If the buyer did not sign for it, then the merchant does. That's the idea, anyway.
Of course most products purchased online are delivered without requiring a signature and I don't see this changing, bitcoin or not. Smaller ticket items are generally considered not wiorth the hassle.
Also, however, customers can seek a chargeback for other reasons, such as the product not being as described, or being damaged.