Hey Tim, with all due respect... you are in fact correct, however we are talking about installing lighting on a structure here. It is really important to pay close attention to regulations, codes, ordinances and listings when wiring on or in structures. Altering any UL listed lighting fixture on site will void it's listing and place the contractor at risk. Much better idea to use products that have been specifically designed and listed for the application.
Also, Contrast offers the shortest retro can on the market at only 3.5" deep. Great for those really tight places where no other pot light will fit.