First thing that comes to mind is Chinese steel and what percentage recycled scrap was used. Perferations in the rolled steel may become more prevalent with time since that area is subject to high temperature swings.
I'd photograph the hole from both sides (high rez if possible) and sharpen the image to bring out any corrosion issues. If you don't have the software send me the image and I'll sharpen it and brighten the image. A good picture is hard to argue with.