HI Jeff,
That's all very good speculation, as well. You'll see I added a bit of speculation as an ***EDIT*** to my last post.
I would contend that the 3 acres next to the clubhouse was a logical and obvious choice for a number of reasons including 1) a nice creek, 2) ingress and egress to both sides of the clubhouse, 3) providing more width at the junction of the "L", 4) unimpeded access to the rail line 5) additional acreage for golf holes near the fixed point clubhouse.
As far as the Barker routing, I'm not sure it ever made it to Merion. It was sent to Connell, and in the same July 1, 1910 Site Committee report to the Board I copied above they embedded a copy of Barker's letter on a Site Committee report, but didn't refer to the routing also being attached.
They simply said that; "Mr. Connell, on his own account, obtained from H.H. Barker, the Garden City professional, a report, of which the following is a copy:", and then proceeded to type out the brief Barker letter.
No mention of an attachment or enclosure.
Oh...Barker did tell them that based on his single day visit that the land was "in every way adapted to the making of a first class course, comparing most favorably with the best courses in this country, such as Myopia and Garden City", and went on to add that "from my experience I believe that proposed course could be constructed at less expense than any I have heretofore gone over."
I bet he said that to all the girls!