Of course things vibrate when they are struck, how do you think sound is conducted? A metal that has the property of flexing will indeed, flex. An organic, fatty, and bulbous tissue will indeed wobble, because it's not necessarily anchored down but more so attached at various points along the muscles of the skull.

Your points do not prove anything, at all. A golf ball does not flex, but shatters. Can you flex a piece of chalk? No, it shatters. Different materials have different properties (duh), it's evident the object in the gif is not actually a real golf ball.