It's all very well being legally in the right. ENFORCING one's legal rights through the courts is something else altogether, especially across borders.
So even if a person is actually legally in the right, financing an international law suit, winning it, and then collecting any costs and damages from the other party is something else completely...
So lets say you WERE to own a few hundred Dollars worth of something, and the client was on the other side of the world, are you REALLY going to launch an international lawsuit and pay $ thousands to enforce your rights? Especially without any guarantee that you ever see a Cent even if you win? That would only make any practical sense in the tiniest percentage of cases.
I apologize for the time it took to obtain the response and post it here.
Once a freelancer has been paid in full, ownership rights transfer to the client. If the freelancer then issues a refund and the client accepts the refund, the ownership transfers back to the freelancer. If the client doesn't accept the refund by letting Upwork Customer Support know, then Upwork will return the funds to the freelancer and the client will retain the ownership rights.