Quote: ANY case open against a seller - no matter whose favour the dispute is resolved in - will be counted as a defect against the seller,

To the OP - Have you read this?

http://sellercentre.ebay.com.au/ebay-for-business/seller-performance-standards

Note this part:

Cases found in your favour don't count. Buyer protection cases are used for the US, UK and German seller standards programs. Any case that escalates to eBay or PayPal for review and is found in your favour, or found to be no fault of the buyer or seller, won't count against your performance rating. It won't be counted as a defect and it won't count toward your percentage of cases closed without seller resolution.