Kyle-
Did you count both courses at FC?
No. Should I? That would raise the average to ~0.156
I'm sure many would argue for the addition or subraction of a handful of courses in the area, so let's just say the figure is between .100 and .200.
I'm willing to bet that a lot more course have been built around Scottsdale (sandy soil, right?) than Pinehurst since 1960, but likely with a sub 0.100 batting average by the reckoning of the treehouse.
So I'll ask again, where does the batting average of 30 or more modern courses within 30 miles of one another clearly (above 0.200) exceed that found near Pinehurst?