As a buyer, you can't get defects, only sellers can. Even if you decided now to leave him a negative, he'd still only get one defect from that transaction.

Even if the request is "normal procedure", most sellers would still prefer to bypass "normal procedure" and handle it themselves. Silly seller! I've had to give 3 refunds since I started selling a few years back. All 3 were done without the need for a request. Both buyer and seller were happy with the outcome!

You tried your best to try and get resolution with the seller, but he left you no choice but to open a dispute. His loss, his defect!