No, he has no use for the rocks other than to show the example. To him, they were simply rocks to be used and nothing more. Her question does strike some interest and if she examines it enough she may understand his magic more. She will find, in any case, that one rock is inside of the other though it has not grown in size or changed features.

"I hadn't really thought about that, if I am honest with you, Miss Mordio. My magic works as it is intended." In his world, he had the ability to manipulate it. If he wanted to fuse to things together over into each other, it would simply happen.