Kirk
You are right. Lillian Gardner's economic background really does not impact the story of William Flynn. I think the reason Wayne and TE played up the poor boy marries the rich girl angle (mistakenly) was because they thought it made from an entertaining story.
However I do think it is important to correct the misinformation, one, because obviously you want to be as accurate as possible in telling the story of his life, and two, I think it goes to the reliability of Flynn's daughter's information. I believe she is the source of a lot of the misinformation.
This is the story of Flynn's early career as told by Wayne & TE (from the article on Flynn in Golf Architecture Vol10). Flynn was a great athlete at Milton HS, and they note he played football. This is confirmed in the Boston press, although I'd say he was most accomplished in basketball and golf.
They claim the summer before his senior year (1908), the 17 or 18 years old Flynn taught tennis at Lake Placid. I question this. There is no reference to Flynn ever playing tennis in the Boston papers and in June, July and August there are reports of Flynn playing golf in local events.
After graduating from HS in 1909, Flynn turns down a scholarship from Williams College, amd marries Lillian Gardner on August 3, 1909, and they move to Heartwellville Vt. I don't know anything about Williams, I do know it was reported on June 24, 1909 that Flynn would not be competing in any more amateur events because because he was turning professional. On July 28, 1909 it was reported Flynn was enjoying himself as a professional at Lake Placid Club.
That must have been a short lived position. In 1910 the US census has him back in Milton, with his profession listed as golf teacher, most likely at Wollaston, where his neighbor was the head pro. Lillian Gardner is living with her parents in Milton in 1910 as well. As of yet they were not married or living in Heartwellville.
Wayne & TE claim Flynn designed Kilkare in 1909, right after the newly weds moved there. End of story, next stop Merion. The marriage of Flynn and Gardner was announced in the Boston Globe Oct 8, 1910. Its unclear what was the exact date of the marriage. The Kilkare project did not begin until 1912. Reports mention Pickering was in charge of constructing the course, I have not found a mention of the architect.