I tried to figure out what you're talking about. While the terrain loads the cursor doesn't move but before and after is does.
Except: I have no other controllers other than the mouse connected at the moment and when I jump into a plane on the runway the cursor disappears. The video about flying with the mouse runs on the clipboard but there's no way I could find to stop or close the video, or check the "don't show" box. But when I shut down the game and restart it, it's fully normal again until I go into a plane.
Something I noticed is that the mouse GUI is not mapped into the keyboard, there's four options for that.
Another thing I would have tried is the key to toggle the mouse on and off. I thought it was "H" but that did nothing, not alone nor with ctrl, alt or shift.
One trick to try is to shutdown your Windows by keeping the Shift key pushed down while clicking Shutdown. The next boot will then start with fresh settings instead of potentially corrupted ones. Worth trying, takes only a minute...