I thought the Gen 3 19 I picked up a few weeks ago was a fluke but the new Gen 3 17 I just brought home also has a 6.1mm rear.
Benchrest your gun to know the "correct" sight picture for your sight combination. Based on the image in post #6, you may have a gun that prefers 12 o'clock sight picture (or 6 o'clock hold), instead of the standard Glock dot-covering-the-target "combat" sight picture.
You may be lucky in that is what you normally do, so before changing the sights out, do some benchrest and freehand testing.
View attachment 991949
There is no such thing as "the one" sight picture -- the "correct" sight picture is determined by the sights installed, not the user.
On a pistol, because the circle is so large, and things are short range, perhaps-- those images are just representative. But on iron sights on a rifle, that is a common sight picture when the circle is a dot in the foreground. So "ever" in you statement is not correct.Image number 1 shouldn't ever be an option. 2 and 3 are the only acceptable sight pictures as far as I'm concerned and yes, standardization should be expected from the manufacturer.