This isn't about the Power Saving Mode itself, it's about that screen it shows whenever you toggle Medium Power Saving on or off, it's useless because everything it does is instant and it's just there pretending to be doing one thing at a time, I can ignore that screen by pressing the home button or multitasking button.

It's not like the Ultra Power Saving Mode, that actually has to change the Android Launcher, disable sensors, etc and that screen cannot be ignored, you have to wait.