Dan,
He really was, along with Tom Bendelow.
Bendelow worked more in NYC and the midwest.
Findlay, after his earliest course in Nebraska in 1885, worked mostly from Maine to Florida, leaving NYC and the immediate surrounds (and most of upstate NY) to guys like Willie Dunn, Bendelow, Willie Norton, Mungo Park and other Scottish professionals up through about 1910.
Once Findlay settled in the Philly/NJ area in the mid-teens, he built a bunch of courses here after WW I, and continued through the mid-30s.
He did do most of Coatesville, although the club opted to save money...just using his design and doing the construction work themselves.
There isn't a single golfer in the Philadelphia or southern NJ area with any experienced variety in courses who hasn't played a hole designed by Findlay.