Well Joe, that's certainly proof enough for me.
Seriously, do we even know when William Gordon began working for William Flynn?
This whole Philmont attribution is interesting to me because as of about 18 months ago, it was believed that the South course was designed by Willie Park circa 1908 with Flynn on the North course in 1924.
Since then we've learned that John Reid did the South course, which was then significantly revamped and improved by Henry Strouse and Hugh Wilson around 1915-16. Given Wilson's close ties to Flynn, that could have been some of the reason for the Flynn legend, but I find that unlikely because Flynn was still involved heavily with the two "new" courses at Merion at that time, as well as working on changes on the East course to get it ready for the 1916 US Amateur.
We also know that Strouse did most of the work on the Park plan "on the ground" for the North course. Might Wilson have been there helping him at times? Perhaps with Flynn?
In any case, I'm not saying that William Flynn was not involved. Certainly we have learned a lot just in the past year...for instance, who knew prior that Hugh Wilson worked on Philmont South??
It's just that based on what's been uncovered to date, it's certainly about the flimsiest circumstantial evidence one could possibly hang a belief on.