He is literally sucking her clit. In my experience that is so intense that a woman has to make some kind of movement. She just lays there, that ain't natural.
I recently started getting close with a coworker after i caught her in a bathroom stall talking to another coworker about turning his daughter into a bbc slut if she plays with him. I could instantly hear her gagging on him and then him fucking her. After he left the bathroom. I went in the stall she was in while cleaning up and without thinking, gave her all my daughter's information as she was gagging on me.