I get your reasoning as to why it might not work, but mine works fine with a 50 yd zero out to 200 yards. I have also shot it out to 260, 300, and 340 with minor adjustment on my hold. Can't explain as to why or how.
Are you using a fixed front sight, or a front sight with adjustable elevation. I have an image attached to my post. in it the front and rear circles are lined up. What happens when you align the 2 circles is the post isn't centered. Most people will just put the post on target without making sure it's centered in the rear aperture. As illustrated in my image the point of aim goes out in a line almost parallel to the barrel from the front sight, instead of on an angle like it would if the post was centered. In my image i have a line for where your point of aim should be, and where it actually is because of aligning circles.