I think that is just a characteristic of the ACOG design. Our team runs the TA01NSN and we see the right reticle fuzzy when the center is in focus, making the right duplex bar seem to get bigger as it runs to the edge of the scope.
Also if you move your head up and down relative to the scope the Left and right of the horizontal reticle will appear to move up and down opposite each other in a see-saw motion.
Someone once told me it was a prism thing, but I do not know if that is some G.I. B.S. or not.