It is up to the buyer to claim unless they return the item and packaging to you with the green claim form filled in to assign the right to lodge it to you. I can't imagine why you would want to waste time and money getting a broken item returned if you are satisfied the item cannot be repaired and resold.

I believe the new ebay process does not cover damage in the post but Paypal certainly still do so.

If your buyer will go to to the PO and put in a claim then you are out of the woods unless they are very dishonest, if AP refuse the claim then by inference your packaging was not up to standard and whatever ebay says I would refund the buyer in full.