OK I understand what you are saying as far as it is 5.5 - but like you said the screen changes depending on what you are doing.
And like I said the only way I see the entire scenn being used is during photo/video. So when you text, make a call, go online, go into settings, etc, etc, etc the screen is NOT full hence Not 5.5 correct???
Am I overthinking this/?? I ask this question because looking at some other phones the capacitive buttons are on the bottom and the screen is then, as you say, Not changing everytime you do something.