The high ground is the desired position because you have a greater view and more ability to plan the strike. Also no one ever looks up for some reason. There should be perhaps a slight buff to hit due to this, but it would make more sense to have some sort of penalty on the person at the lower elevation.
Shooting anything from higher up like a bow or rifle has advantages like better field of vision. You have a wider angle compared to ground level or shooting from below when the target is above you. Also if the target is below you up above isn't part of their normal line of sight.
I didn't really delve into the bonus/penalty of the lower person in my OP. These quotes sound like reasons why the person below should have a penalty, but not necessarily that the person above should get a bonus. More field of view is great for spotting more enemies, but that's irrelevant once you're targeting them.
Also keep in mind that if there isn't actually cover for the person above, the same thing happens where they become a smaller target to the person below as the angle steepens.
