PM,
To parse, I believe it was an "Afterthought" because I do not believe an extra-pleasure feature took primacy before a solid routing could be identified. But once the 18 hole routing and the necessities of the clubhouse and other faciilties were incorporated, in whatever stage of design, the feature was able to be availed.
This could even be true even if there was a "client demand" of a 19th hole...but its ultimate actual placement wouldn't, I do not believe, make the 18 hole course slave to its requirement.
In my Armchair Contest entry, I knew I wanted a 19th hole, and have placed one, but I knew it would likely reveal itself (being a small acreage) once the mass was settled.
cheers
vk