We agree that giving advantage/disadvantage is strong. But I don't see why arguing about +2, although I prefer that to an advantage.
Because the devs clearly have their mind set on "rewarding the control of higher ground" and they have been vocal about it (in interviews, I mean, since they hardly talk to the community to begin with) so we may as well compromise on something that is less disruptive.
Because the worse thing about "Advantage for height" is not even just how powerful it is (and IT IS powerful, to the point of being over-tuned, as we said countless time). No, it's how implicitly pointless/redundant it makes a whole lot of class abilities and spells, since "Advantage" doesn't stack.