I'm not following your thought process....
AR-15 iron sights are approximately 2.7" higher than the barrel's bore. Scopes can be a little higher or lower depending on ring's height.
Your line of sight is straight, the arc of the bullet in flight is not.
If I zero 1.25" to 1.5" high at 100 yards my .223 rifles will be dead on at 200. At 50 yards I should be a little lower than the aiming point because the bullet's slight hasn't made up the 2.7" bore v. sights height difference.
Iron sights work the same way, provided you use a "Navy hold", meaning covering the target with the front sight, splitting a bullseye target along a horizontal line.
I use a six o'clock hold with iron sights, otherwise known as "a pumpkin on a fence post". This zero has me printing on target approximately 2.5 moa to 3.0 moa above my point of aim. This allows me to see the target I'm aiming at because it's directly above the front sight post, not being obscured by it.
The only time you need to consider elevation inputs is when the shot angle is in the mountains or other high elevation platforms where the angle up or down is relatively extreme and there is increased distance to overcome.
A nine foot rise in the prairie does not a mountain make.