"Unable" or "unwilling" are two different things. Of course they have the ability to reverse a charge if they wish, it's strictly a matter of YMMV depending on the property and FD personnel. The gist is, according to the T&C of the certs, they don't have to. But many have been successful (including myself) at doing this.

One tip: Don't tell them upfront that you want to use the cert. When I have done it, I very innocently and politely asked them if it was possible to reverse the amount charged because I wanted to use a "different payment method" or "different credit card". After they agreed to do it and it was processed, I produced another credit card... and a couple of certs. They did not have any problems processing the new payment.