But the up and down really consists of two user actions, pressing the mouse button, and releasing it again. See drag-and-drop for example, where that distinction is important. It’s even important for simple buttons: You can generally abort a button press by moving the mouse pointer outside the button area before releasing the mouse button again. In that case, the button action isn’t triggered. The pressed-down state visualizes that the action will be triggered when you release the mouse button while still in the button area.

Animation is when more than one consecutive step happens on it’s own. I’d argue that even tooltips appearing and disappearing after a timeout doesn’t constitute an animation, because the disappearance isn’t immediately consecutive with the appearance, and (maybe more importantly) the intervening state of the tooltip being shown is meaningful to the user as a distinct state.