Keep in mind that the model in question told the studio up front that he was a bottom. When he arrived at the shoot, he was asked to top. He told them that it would be difficult but he would try. It didn't work out. Then they asked him to top again. Again it didn't work out.

If a studio hires a model as a bottom and then asks him to top and isn't happy with the results, they have no one to blame but themselves. Good planning and casting for a shoot prevents these sort of problems from happening.

Under the circumstances (where a studio asks a model to do something outside of what the model is comfortable doing) then it's not at all unreasonable to pay the model for the attempt. And besides, by the studio's own admission, they agreed to pay him.