There's no way to really know how eBay can or will contest a chargeback, as it would depend on their contracts with payment processors etc. I suspect for low value orders, they just wear it, for higher value orders they would be more inclined to contest if they had compelling evidence - their policies state that sometimes, after a dispute has closed, they might come back asking for more info from a seller, which is likely there for the times they do contest a chargeback (this can actually take a couple of months). There would be a cost - benefit ratio where orders under a certain value just aren't worth investing in fighting a claim. They would, however, have access to far more information about a buyer than the average seller receives, though (personal info, IP addresses, whether that card / PayPal account etc has been used for many previous purchases from the same account at the same IP address and the orders were all going to the same delivery address etc, which would help them make a much more compelling case than any of their sellers could).
The main problem (in general) is the laws card providers have to uphold when unauthorised use chargebacks are filed, which do make fighting them very difficult, another big issue is payment processors forcing that liability onto the sellers in card-not-present transactions (i.e. generally speaking, where the card can't be physically sighted by the seller).
A very eBay-specific issue, which may not be all that relevant to your case, is the change in payment records / details once sellers migrate over to managed payments. For years, when a buyer has purchased from an eBay seller, the records say "payment to [seller name]". When a seller switches to MP, it just says "payment to eBay", and PayPal records don't even have seller or item details. I feel like this is a recipe for disaster, as some people just won't automatically twig or connect the dots, instead they'll just wonder why the heck there's a debit from ebay for $X. For a larger purchase, maybe this won;t be an issue - if I buy a laptop on eBay for $784.99 and see that "eBay charge", I'll know straight away. If someone is buying multiple items consistently and in amongst a bunch of transactions they recognise immediately / intuitively, then see "eBay" $20, they might not even think to check if it matches with something in their purchase history. These lower-value transactions are also less likely to have tracking.
Anyway, you can report the buyer yourself to ACSC, if you want to - as there was no financial loss, they won;t do anything for you, but the report will go into their database regardless. Info is typically shared with police so the buyer will be on record as an involved party, and may even wind up on someone's radar if they rack up multiple reports.
