Then I realized that what I was looking at was a removable mullion that was not mounted behind the doors as it was designed, but between the doors, leaving visible gaps along the lock edge of each door. The black spacers are needed because the backset of the panic hardware was calculated based on the normal (and correct) mounting location of the mullion.
I know that some of you are hysterical right now, and others are scratching your head. It’s sort of a “you had to be there” kind of thing, without any of us actually being there. In a nutshell, the frame was ordered a couple of inches too wide because someone didn’t understand removable mullions.
You can learn more about removable mullions by clicking the graphic on the right, and there is a video here. I have to say…I have run into lots of architects who had a tough time understanding how a removable mullion works, but I have never seen one installed like this.