Yeah, but this is what it actually says:
If you need to run your production system on Windows then IIS7 will give you the most stable and best performance.
So it seems to be recommending IIS7 specifically, IIS 7.5, IIS 8 and IIS 8.5 have come out since then. So it is a bit like saying you should run this software on windows vista for best performance. IIS7 is old software.
I guess I'm asking, have the IIS team given up on PHP performance or is this recommendation really out of date.