The idea is that there would be an option that when enabled would cause full screen playback to happen every time the play button is pressed (either for the source or program monitor depending on context). When playback is stopped the layout would revert. Essentially an auto "Toggle Maximize Monitor" mode.

This is not a feature intended to be used always, but when doing a final polish pass I like to view my sequence full screen and then stop to make changes. Toggling maximize monitor off and on just creates a lot of extra button presses during this workflow.