Developing Point of Aim with Red Dot Sight Handguns: Watch Sage Dynamics
It is common for people new to pistol optics to want to use their iron sights to find the dot of their optic. That short cut is often a hindrance to properly learning to use the dot Optic as the primary sighting device. The trick is to focus on the target and use your presentation to put the gun between eye and target. It seems many new to pistol optics start off using their iron sights to find the dot and then never unlearn that bad habit.
With iron sights, you must focus on the front sight. With pistol optics, we need to change that and focus on the target, with the dot superimposed over it. A proper index, draw, and presentation will almost always result in the dot being over the target.
Co-witnessed sights make alignment similar for irons and the dot. The lower the red dot, the less you need to change your old iron sight presentation and head position to find the dot.