POI is a factor of grip, recoil, and bullet velocity. A mechanical alignment of bore and sights is not necessarily a useable sight setting.
Shooting one handed versus two handed changes the point of impact also, because of the greater resistance to recoil when shooting two handed. The farther the distance, the greater the effect. Shooting 300 yards with the glock 19 requires a different sight picture one handed compared to two handed. It appears
to shoot "flatter" one handed, since it requires less sight held up.