Jamie:
That's Mr. Finegan's account of how the 13th came to be and his account is basically a reiteration of Mr Shelley's club history book. Knowing now how that idea on #13 first occured to Crump would be tough to document, to say the least. We should realize little things such as that no one then could feel the significance of when they happened.
The interesting thing about holes #12-15 is how long they stayed unfinished after the course was in play. Part of that, in my opinion, had to do with how easily PVGC could play as an 18 hole course with only fourteen holes in play (they played 1-4 a second time and were at the clubhouse).
I also believe Crump basically designed himself into a box by finishing and putting into play 14 holes without first settling on the details of the four remaining to be done (12-15) and that, again, lasted for a couple of years. The design of those holes (12-15) is Crump's although he never felt comfortable about #15 apparently and his ideas for #13, on paper anyway, was slightly different from the way it is now (bunkering particularly and the way the approach was to be played).
PVGC took approximately ten years to finish all 18 holes. Some apparently were getting impatient and asked Crump when he planned to finish the course. His documented answer was, "NEVER!" (he apparently intended to tinker with it for the rest of his life).
John Ott, who admires George Crump greatly, sometimes says, half humorously, it may have actually been a good thing for the course that Crump died when he did. In reality, I, personally, don't agree with that. Had he lived some holes surely would've been different than they are now and we even have a glimmer into how they would've been. A few of them I actually think they should consider doing the way Crump visualized them and intended to treat them.
We believe now that it was William Flynn who oversaw the construction of 12-15 after Crump died, probably particularly #13 & #15 to Crump's design. Merion lent Flynn to PVGC for an extended time during that period of the final construction and grown in of those final four holes.