Through some friendly research assistance from folks in the Pinehurst area, I've been able to determine that Wanango is most definitely "not" a Donald Ross Course, but is instead nine holes from Tom Bendelow (design 1913/opened 1914) with A.W. Tilliinghast providing an additional nine and reworking the first nine (design 1917/opened 1919).
The information about Wanango in the Tufts Archives was a page from Samuel Y. Ramage's autobiography where he describes Wanango's course origins as I described above. Ramage was one of the originators of Wanango and a long-time club President.
Ramage also had a house at Pinehurst and wintered there through the period, which is probably why his recollections were included in the Tufts Archives in the first place. Folks speculate that it's likely Ross may have visited at some point, likely while the grounds were being considered for purchase given that Ross and Ramage were good friends, but no one has any solid evidence of that.
Thanks to everyone for your help in solving this mystery.