AWESOME
This is great . . I can change it back & forth YAY.
You guys were dead on . . .
When you have the second display on 'bullseye' (master display) as well as the first, and the two displays are at a different resolution, it causes the main display to 'see' the desktop as if through a 'looking glass' (with view size and magnification proportional to the ratio of the two monitor resolution settings).
When the second display is an "exact duplicate" of the first , it appears 'normal' on your main display.
I do not know if this is an intentional feature, or an anomoly, but I like it. It is really weird to get used to, but once you do it has potential for multi-tasking . . . you can almost treat it as using an array of 4 monitors, and by moving the mouse to different corners you change focus to a different one of the four. With the right mouse set-up it can be very convenient once you adjust to it.