Touchpad = flat mouse.
It makes mouse events as if it was a "real" mouse...because it basically is.
The thing with tablets/phones (touch screen devices) is that, unless they have a pen/stylus with certain capabilities, they can't simulate a "hover". Probably varies by device.
Taping on the screen is a left-click. Tap-and-hold a long time is like a right-click (at least in some cases). But there's no way to move the pointer without a click. Dragging your finger on the screen is a touch-event, not a mouse event, or gets translated with a click-drag mouse event. So maybe some devices have a way to translate the events differently and make a mouse-cursor movement (like with a stylus moving the pointer).
People on touch screen devices might try tap-and-hold and see what it does. Probably varies by implementation.
So I guess it all depends on the device. Touch input has messed up 1/2 the web! Grrrr. (I'm really just kidding here). It is a PITA for developers though...