Ebay is profoundly prejudiced in favor of buyers and against sellers. That is probably a big reason for its success.
I am approximately equal parts buyer and seller. It has been my experience that about 2%-5% of transactions go bad, for whatever reasons. That is the "cost of doing business" on both ends.
The item is clearly in the hands of the seller until it leaves his hands. His honorable duty is to describe the item accurately, package it securely, and ship it properly to the address supplied by the buyer.
When the item arrives in the hands of the buyer, it is his responsibility to accept it, if it was the item he ordered, described accurately and delivered properly.
There is opportunity for various kinds of dishonesty on both ends, and opportunity for all manner of mishaps during shipping.
The gray area between leaving the seller's hands and arriving in the buyer's hands cannot be placed on the seller, in my opinion. If I sell you an item, package it carefully, and post it properly to the address you provided me, I have fulfilled my obligations. If the Post Office loses it or damages it, then I, the seller, do not owe you a replacement or refund.
Personally, I have given numerous refunds and replacements, out of "the goodness of my heart", and only twice have I ever received replacements, for which I was quite grateful.
As far as I am concerned, a seller who replaces an item lost or damaged by the shipper in shipment is doing so "above and beyond the call of duty"