Anyway, the Sub is supposed to be the one that’s actually in control for this kind of thing

I think there’s a better way to put that. It’s often called a power exchange. Both people involved can rescind consent at any time, and there’s also negotiation that happens before scenes to set up expectations and limits, but I don’t know too many subs that want to be in control of a scene. My experience is they want to give up control in a way that is safe.