The in-game setting has some undesirable properties.
First, it can only be assigned to a proper keybind. It can't be assigned to CTRL.
Second, it will actually show the wrong location if you do anything that involves the pointing finger cursor, such as confirming a ready check with num4-num0 (cursor left, confirm). The in-game mouse sonar will tell you your mouse is where the pointing finger cursor last was (center of screen in the /rcheck example), while the Windows mouse sonar will tell you where your mouse cursor really is (wherever you left it before the /rcheck appeared).
(not captured: after the Teleport window closes, the Windows mouse sonar shows the mouse where it actually is, in the upper left corner)