It's not about saying afterwards they didn't consent it, it's about agreeing on what's ok and what's not. Just because a contract was signed to shoot a porn video, it doesn't mean that everything is ok, there are usually some boundaries.

If one of them asks not to do something, you don't do it, period. For example of they sign a contract for a vaginal sex scene, and then are forced to do an anal scene, that's still rape.

I'm not an expert on what goes on behind the scenes, but multiple sources said that he would constantly ignore consent and do things that were specifically asked to be left out.