If I understand correctly, setting that to “false” stretches the overlay to the viewport and setting it to “true” stretches it to full screen.
Except setting it to true makes no difference and is still just stretching to the viewport size.
Right now we have to mess with overlay0_rect to get an overlay to “full screen” i.e. the screen resolution. This is less than ideal if we are using the same screen resolution but different viewports.
If it did work then overlay0_rect could be set to “0.0,0.0,1.0,1.0” plus 1.00 scaling and it would give us perfectly placed borders— as an example.