Hagrid said that from his meeting with the miraculous boy and a little trip via Diagon Alley, that he seemed very quiet... Which is complete nonsense! Impossible! The Potion Master is sure that the boy’s loving family has already shown him everything, so he wasn’t too excited and loud, moreover in the company of someone as weird as that forester. Nothing can be exciting enough for this dump Potter, that is the only reason why the future Gryffindor retained minimal propriety and didn’t shout around the whole Alley about his arrival. And the half-giant was too drunk to pay attention, soaring in the clouds about the new forbidden creature he had bought. But equally, Snape agrees that sometimes the overgrown can be useful, for example, when he is able to talk to the aforementioned beasts and get rare ingredients from the Forbidden Forest (actually that is the only thing he is good at, according to Snape).