This one of those cases where eBay's efforts to make the marketplace more secure and trusted have had unintended consequences.
Scammers know that sellers have very little recourse in a case like this. Things don't end well for sellers in a he said/ he said case like this. There is no way to prove what actually took place and eBay tends to side with the buyer to achieve their higher goal of marketplace trust at the expense of the seller.
eBay fails to see that it's just as important for sellers to trust the marketplace as it is buyers.
When transactions go south, the burden falls 100% on sellers. eBay invests nothing in reducing anyone's risk or loss. There are some minor protections but not enough. When does eBay intercede on a sellers behalf?
In this case, shouldn't eBay send an email to the buyer that falsely claiming an item did not arrive is fraud., eBay takes these cases seriously and if it turns out that the the claim is fraudulent they will fall up with law enforcement. The same would apply to sellers too.
Since we can no longer leave negative feedback for buyers there is no way to alert the community to scam buyers either or to have them fade away after a few transactions as their FB will be get the unregistered.
eBay enforces the INAD on every transaction leaving a lot of potential liability on sellers for the whims of buyers.
Was it better in the old days when return policies where all sellers choice? Maybe? You can't implement an INAD or empty box scam if there are no returns or returns only upon receipt and acceptance of an item. Sellers can compete on return policies and buyers can make choices on who they deal with based on numerous factors.
Now eBay can even return money right from a sellers account.
eBay has become, judge, jury, and bank. Yet they have little, if any, of their own skin in the game.
