Will flipping the rear sight aperture from large to small diameter hole maintain the same POI?

The reason I ask is that GG&G offers a MAD sight which claims to have the same POI in any position.  If this were created to solve a problem, is the standard sight a "problem?"

Depends on what distance you establish your zero at and on which apecture, but yes it can substantial in difference.  For what I do (patrol rifle) and the fact that my folding iron sight is a backup to my aimpoint, I replaced the standard military sight in YHM folding sight with an Ashley same plane sight.  this gives same POA/POI on each but allows for the large apecture for low light or close work (ghost ring) and the smaller for more fine work.