No Tablet PCs do it as soon as you take the screen out of the 'laptop' position, and they have another button that lets you switch orientations. No accelerometer is used. Even if it was an accelerometer, obviously the interface for rotating the screen via hardware is present, and it should be easy to replace the accelerometer with a switch.
But that's a whole other topic anyway...
And no in Windows all the settings are correct, I just can't find a way to do it outside of windows. Of course I could always get another GPU and connect the side monitors there, but that's a last resort.