Will actually thinks he's benefited as much from these sessions as she has. In all those years learning on his own, he perfected form and technique, knew his own strengths and honed his body, but Elizabeth -

He narrowly parries the side cut, leaps to the other side, and bring his words around fast at neck height.

- but Elizabeth always tries to surprise him. And the better she gets, the more challenging an opponent she becomes. He's learning to adapt to her changeability. Beyond the first few lessons, he's never tried to tame her to his own form; he alters his own style to fit.