Allow me to chime in a little here. The early routings indeed had that location as an amazing green site. It could have also worked in TD's final routing, but as has been noted, it was very close to the parking lot of the National pro shop. In fact, part of National's parking area was actually on Sebonack property. Pascucci, not wanting to agitate National members with balls potentially landing in the parking lot and being dangerous, decided he wanted to move the green away to avoid even the possible errant shot....and be sensitive to National membership...which he did with every decision. When the range was moved over closer to the property edge, trees were left on the left side , and realizing that the more dangerous errant shot would be right....away from the National property. It was interesting that when the first tee was being staked out, it kept getting further and further from the National property because an enormous number of balls were all around the original tee location, coming off the first tee at National.
Tom is the one that made the call on the 19th hole location being on that terrific green site....and that is the first I had heard of his explanation coming from Garrett.
However, the idea of a 19th hole to settle bets was always something Pascucci wanted, and it was designed in all the various routings prior to TD's final routing.
In regard to the present location of the first green, I am sure TD will remember that he had constructed a green closer to the present 18th green, and that on a a late visit, as the first hole was one of the last completed, I actually suggested during a discussion about whether that was the best location for the first green, that the green be moved right approximately 20-30 yds., as I recall, and TD constructed a new green in the new location, that is there today. The move all had to do with the natural backdrop of the green, for the water view, and not anything to do with the merit of the green already constructed.
The resulting 19th hole is a terrific hole and works well, from what I understand.