Half of it is to see what the new form feels like and how it reacts to being touched, and half in an attempt to comfort them. Jack lays his hand carefully and lightly on V's shoulder, giving it a kind of slow, gentle pet after a moment. "There. There, you're okay. It will pass." He hopes it will. He assumes it will, because generally sudden transformations like that do in his experience. And, to make sure, "This doesn't hurt you? Me touching you?"