LaserWriter 8500: Erroneous Safety Notice In Paper Tray

I received a brand new LaserWriter 8500 from Apple that contains a sheet of paper in the output tray that reads "Caution - Controller PWB must be installed before shipping to customers. Without controller PWB this machine does not meet safety requirement." What is the controller PWB, and why is this message included with the printer?
The controller PWB refers to the LaserWriter 8500's I/O controller board.

A limited number of LaserWriter 8500 printers were accidentally shipped with this notice in place. The notice is supposed to be removed during the assembly process when the I/O controller board is integrated with the print engine assembly. Customers who receive the notice with their printer can discard the notice and safely use the printer.
Published Date: Feb 18, 2012