Reno, obviously I don't have the answer, but without seeing the installation instructions, I think maybe the presence of the recessed lip around the perimeter of the fixture indicates that the manufacturer intended the fixture be installed with the space available for the wiring. Although, I'm thinking a similar comparison might be when we tighten down the screws of a ceiling fixture where there is normally a gap between the actual strap and the canopy, if the screws are tightened excessively, the canopy could also possible bow or distort and damage the wiring in that scenario as well.
Don't get me wrong, I'm not defending the design, but it just seems pretty standard arrangement as far as wall mount fixtures go.
