Tom MacWood,
I guess off the top of my head in answer to why Wilson didn't reach out to P&O prior to November 1913, there are any number of possibilities.
For instance, the William Evans article mentions that the course is built on sandy loam. At that time, everyone from CB Macdonald to George Crump were under the (mistaken) impression that such a surface was ideal for building golf courses and growing grass.
In fact, the whole nature of Macdonald's letter to Merion after his initial site visit was to put them onto some folks like P&O who could help with inland, clay based soils, which were much different from what Macdonald was working with out at NGLA.
Also, it's tough to tell from the letters, particularly the second one, exactly what Geist was trying to accomplish and whether it was even related to the first course. Reclaiming nearly 50 acres of marshland sure doesn't sound like the Bay course to me....and early accounts mentioned Geist's plans for a second course.
Now, the letter that is germane is trying to drain the five holes that were built in the lowlands because even today those holes stay relatively wet and my bet is they are below sea level. So, it was probably only when they ran into some trouble, or realized that their original optimism about the site wasn't quite well-founded in all respects, that they reached out to P&O.
I mean, Wilson was already deluging P&O with constant letters just based on trying to get golf going inland on clay at Merion, and I'm sure he wanted to be sensitive to the fact that they were helping him greatly, free of charge, yet taking a lot of time to do so. To then introduce another course, on another site, with much different types of soils had to be something Wilson was sensitive to introducing as a topic to these guys. Your own quote of Wilson to P&O when the West course was first contemplated in December 1912 shows that he was a discerning fellow not wanting to exhaust that valuable resource;
"We are contemplating building eighteen more holes, possibly next year, and will still continue to bother you for a while".
Or, perhaps Wilson, being located in Philadelphia at the time when a trip to Atlantic City was a couple hour train ride both ways and already having a lot going on at Merion just did a site visit and layout design of the course for Geist, and then worked with Pickering and/or Robinson on construction, largely from a distance? He certainly had faith in Pickering's agronomic abilities, the man being a grass expert himself, having built according to Alex Findlay literally hundreds of courses by this time.
I just don't see any of this as some great mystery, or beyond very reasonable speculation.