The spec says that mousemove event fires at specific framerate that depends on envorinment. But as I have tested it also always fires right before every mouseup, with the same coordinates. So lets say we have 60 times per second mousemove firing, but if we move qiuckly between those frames and fire mouseup, mousemove will also be generated right before with same coordinates. So it will be 61 times per second. Why is that?