"The muscles in his arms and back trembled as he pushed in as deep as he could go, until all of him was buried inside her. His head sagged and a deep, primitive snarl ripped free. Sparks of light exploded behind her tightly closed lids. His hands burrowed into her hair, holding her head still while he kissed her hard and deep and wild. Then he began to move. Hard, steady strokes that ignited every nerve ending in her body."
— Kaylea Cross (Deadly Descent)
I found this rather explicit quote on Goodreads. And frankly it reminds me of Darth Vader's immortal words "I'm a dictator not a mathematician!"
Logic tells me that first of all it is physically impossible for him to have “all of him buried inside her”, but if he really could do so, when all of him is at this point buried inside her, he can’t very possibly burrow his hands in her hair or hold her head (her brain possibly if he dared to move up far enough).