Unfortunately the documentation here is a bit lackluster. The property is mainly about dealing with the touch events and how to constrain whether those events are reported via the event handlers. If the option is unchecked, then events will not be reported if a touch starts in the canvas and then proceeds outside of the bounds of the canvas. If the option is checked, those events will occur, even if the x/y coordinates are outside of the bounds. Sprites cannot be positioned outside the bounds of the canvas, so knowing that the touches go outside the bounds are only of limited use.