I don't know, whereas screen and display were really just different ways of saying the same thing,and were proper synonyms. These all seem like specific cases where a specific aspect or behaviour is being asked about. I think people are likely to search for "screen timeout" or "screen brightness" so these are useful tags.
Though as the one question in Screensaver makes clear, that whole idea just doesn't make sense in Android at the moment, so it's debatable whether we need that tag at all. But if things like Android x86 take off and we start seeing Android in more devices like desktop-style machines, or when Android is running devices with expensive screens that are permanently connected to the mains power, like TVs, set top boxes and Ouyas then screensavers could become a real thing for Android in the future.