Jordan,
Oakmont was a labor for life for Fownes. He modified, poked and added and subtracted from the course for all his life.
He was into agronomy and turf practices and advanced a lot of the science at the turn of the century. Oakmont's greens have always been amongst the fastest in the world for this reason.
Additionally, his work turned Oakmont from a Penal Nightmare of a course to a strategic gem.
Emil Loeffler and Arthur Jack Snyder are two architects who had worked with the Fownes boys early on and started careers from that experience.
As for Pine Valley, Crump had more contributors than HS Colt, which someone like Tom Paul can get into more. For example, William Flynn completed the last four holes upon Crump's death.
Read some of the "In My Opinion" pieces for more information. The one about George Crump by Tom MacWood (where's he been, anyway?) is particularly moving.