High ground does give advantage in real life combat; and there are plenty of reports of people exerting themselves amazingly for short periods (historical berserkers come to mind).
If you think it's easier to hit a target 100m away from you with a bow when you're higher in comparison than if both of you are on the same level... You never try archery...
In arena such in BG3, you wouldn't have any advantages in real life because most of the time, there isn't any obstacles
When I hunted, I learned things like "leading" my target. There's a reason deer blinds aren't sitting on the ground, but are up in trees, even for archery. Yes, you can get some more distance from a shot, but that's not why you go to high ground, you go to get better advantage, defined here as being able shoot over obstacles w/out having to actually shoot over them. We're not in an arena, we're in natural terrain, for the most part. There are obstacles, even when indoors. Being in a higher position means you can shoot over their cover, or nullifying it completely depending on how high you are. This isn't only realistic, but is reflected in the rules as "Advantage". On a level plane, with the target behind a waist high cover, you have a smaller target than you would have if you were higher up. In the rules, it gives a +2 AC? This has the effect of making the target harder to hit, on a level plane. If you're higher up, you have a larger target, because the waist high cover might now only be knee high, depending on the range and angles. In game, this is reflected as advantage, and it should be clear to see why it is advantageous. This is the one thing I don't miss about table top, aside from when it's at my house, and I have to clean up the next day, rules lawyers, and it's especially bad when they're lawyering away at a rule, with such a poor understanding of what's actually going on.
