I get that this was a surprising outcome for him, and I feel bad for him. But as a business consultant working specifically in fintech, I don't feel very bad for him. Looking at the dates, I also suspect he isn't telling us about the fraudulent payments he did get to pocket.
That software is for detecting a different kind -- exactly the opposite kind to what happened here -- of fraud.
[Edit to add:]
> Looking at the dates, I also suspect he isn't telling us about the fraudulent payments he did get to pocket.
I thought he mentioned that he had worked for "Robin" for two years? And he never says he was paid with a different credit card for the first eighteen months, does he? So as I read it he does indeed tell us about the fraudulent payments he did get to pocket: Those for those first eighteen months. It's just that the legitimate credit card holder couldn't issue a chargeback for those, so there's nothing for Upwork to try and claw back from him there.