I wish it doesn’t. For example, if I run a command that will take 1 minute in a terminal and switch to web-browser to read something in this time, I don’t want that command to pause.
I think the automatic suspend option from Settings/Power is better, suspending all apps.
There is something else that helps (see gnome-session-inhibit). Every app that wants to keep the screen on (book reader and maybe pure maps) will inhibit the screen saver. The user does the same when it interacts with the touchscreen. The user can override this, turning the screen off, by pressing the power button. In addition to this, an app can inhibit suspend. Lollypop, for example, will prevent suspend when playing an audio file. It is even nicer that it has controls on the lock screen, so that I don’t have to unlock the screen to pause/resume/skip that audio stream.
There is something that your ignore (by not closing tabs): the memory. From what I understood, android can signal an app to save its state and than close/kill that app (freeing memory). When the app is restarted with the old state, it might look like it was never closed, not even if the phone has been restarted. On Linux, the closest thing to this are the web apps 