All I know is that its been working the same way for at least 10 years and I switched TVs, monitors, GFX cards and OS (win 7 and 10) during that time without a change in behavior until this weeks new drivers. "App windows are not moved to primary monitor spontaneously" I think that when I turn the TV off now with the new drivers, for a second or so it loses the connection or something. Maybe that tricks windows to move the app windows to the main monitor. Every time I turned off my TV in the past, the main monitor goes black for a split second (like it refreshes the configuration or something). So I'm sure windows/Nvidia drivers have always noticed when the TV was turned off. But now in addition to the split second refresh it also moves the app windows. Maybe now it actually disables the extended mode for a split second and that triggers the move of the windows.