What makes you think there's something wrong with it? You'll find the same diagram on both the Duncan and Fralin sites.
I have seen folks add a jumper from the top left side of the switch (the open lug) to the 2nd from top on the right side (with the blue and white wires) to short the neck coil in position #1. I've never tried that, so I can't say if that makes any difference at all.