Don, no argument there.
My comments apply only to handheld and tablet devices I've dealt with. On computers, particularly laptops, you can most often see that the backlighting is still on, and the screen black, which suggests Quentin's proposition is indeed what's going on there.
Brian - Windows 10 Home, 64-Bit, Version 1809, Build 17763
A great deal of intelligence can be invested in ignorance when the need for illusion is deep.
~ Saul Bellow, To Jerusalem and Back