All of your "read the fine-print" logic can be applied to Handy and Amex just as easily as to Handy and the customer.
eg:
If Handy doesn't like the deal where an Amex customer can request a chargeback for inadequate customer service then they shouldn't accept Amex as payment.
It's not fine print. It's the basic service model. They are very upfront about it. I understand that lots of people in this thread would prefer a different model. But that's not what they offer right now. I'm not for or against it: just tying to add facts to the thread.
eg:
If Handy doesn't like the deal where an Amex customer can request a chargeback for inadequate customer service then they shouldn't accept Amex as payment.