Tom, again, that's simply a false choice and its really a shame you seem locked into a hamstrung stockade of your own prejudiced incredulity.
For whatever reasons, call it snobbery or whatever, but its very clear from the historical record that both NGLA and Merion purposefully eschewed the use of a professional for their golf courses and seemed quite proud of that fact.
Merion did in fact use Macdonald, and leveraged his advice and suggestions in selecting their site and also had him come down just before construction to Lconsider and advise on or (five) plans", in the words of Alan Wilson as clearly reflected in the MCC Minutes of April 1911.
The Minutes, after saying the Committee rearranged the course and created five different plans in March/April 1911, say Macdonald and Whigham came down and "spent the day on the ground, and after looking over the various plans, and the ground itself", determined that if Merion were to lay it out according to the plan they approved ("which is submitted herewith") they'd not only have a first class course but also have the finest seven finishing holes of any inland course in the world.
Of course, one has to wonder if these were indeed plans CBM had himself created supposedly six months or earlier on some topo map as David would have us believe why CBM would then have to "look over the various plans", or even come down to look at the plans again in context of "looking over the ground itself", or why he couldn't have made up his mind over the course of the previous nine months where he was supposedly diligently working on a routing for Merion via a topo map while trying to get NGLA in condition and the club opened, but that's some of the willing suspension of disbelief that's required to actually try to digest this stuff.
Similarly, to believe your theory that Barker routed the course in December 1910, we'd have to throw out every other single piece of contemporaneous evidence or news account ever found, but what the hell, why not.
But hey, I guess that's what revisionist history is for...to keep conspiracy theorists occupied with their tales of intrigue, conspiracy, and paranoia.
As far as the history of Pine Valley, there is a thread that Joe Bausch put together that documents what was happening on that course in real time as it happened.
You should read it.
You should also be aware the Colt visited Merion and Seaview, and they were proud to have him.
It's no wonder that Alan Wilson lamented in the early 20s that the US simply did not have a professional architect as good as Harry Colt. THAT was the prevailing thinking in tow among these guys...they simply weren't impressed with much of the junk the pros on these shores had turned out, Tom.