I agree with Alan and Craig as well. I think it's over blown and really isn't even visible when looking at normal sized prints shot at f22 and compared to f5.6 prints. Here's a little test i just shot.
I'm comparing 100% enlargements from f5.6 to f11 to f22 from left to right.
I used an AF 105mm f2.8 Micro on my D800. I was at 10 feet from the subject and used flash from a SB800 synced at 1/250 sec. ISO was 400. There was no post processing of any of the images, not even down sampling.
I can see a slight softening of the image shot at f22, but only at the 100% cropped image. I don't see any softening at f11 and would consider this excellent performance in a studio setting.