This would be good behaviour to make Edge on a Surface Pro in tablet mode act a bit more like browsers on iPads. When you scroll with your finger, the interface at the top of the screen (and perhaps the windows taskbar at the bottom) minimise to give you the most screen real estate possible. It would help make tablet mode in Windows feel more useful as an internet/media consumption device. A tap on the screen or a scroll up will bring back the bars to full size.
Would something like this be possible? Of course it could be an optional behaviour that people could turn off if they wished.