This is a bit of an understatement. If this really bothers you and you want to fix it then you have to figure out the resolution of your TV during boot. On my TV I can press the “info” button on the remote and it shows this information (mine is 1366x768 during boot). Download the image below (this is NOT the same as what comes with OSMC) and resize it to your boot display resolution if your display is something other than 1920x1080.