While true, all of this matter little. What matters is that this height advantage/disadvantage adds too much to the strategy to be just abandoned. I am pretty sure Larian is smart enough to understand that and ignore this thread even if it gets to 100 pages.
My experience was that it didn't add to the strategy, it clobbered it. All other strategies quickly became obsolete because it was the easiest to pull off and came with the most benefit. So yeah, changing it to +2/-2 would be MUCH better, but maybe (and I'm fully making this number up) 75% of fights in the game shouldn't have verticality. If it wasn't the best choice almost every time I think the strategic diversity of the game would be better.
I made the OP because I wanted a good visual that explained how the steeper angle decreased the viable target area and it was just a fun challenge. I think the OP here
Remove Height and Backstab as Sources of Advantage/Disadvantage makes the best argument for why the bonus shouldn't be advantage/disadvantage.
Anyway, it's been a fun discussion
