I have heard that some studios have contracts like that. If an actor doesn't perform (cum or get off) they don't get paid. A model recruiter that I hired form a fairly large membership website asked to have our contract changed to have wording it in the basically said that a model would not get paid for the shoot if they could not perform. Please note we are not using this form, I think if we were paying 2 to 3k per scene I might be, but at the moment we are not so I'm not to worried about it.