Hillenbrand confirmed with Irwin's guy (Gentry maybe?) that they did not work on that green. Here is another coincidence. Both courses had holes named Oasis and Crater. Also from contemporary (almost) scorecards.
Man, maybe my memory has faded. I'm sure the first Biarritz I ever saw was at SLCC. It kind of stunned me. That was well after I'd played Forest Park a number of times.
Let's see, Crater on SLCC is probably #12. Guessing 6 or 18 for Oasis. No clue which holes at Forest Park had those names. btw, the green complexes were probably the weakest part of the course.
I've told this story before, Nigel, and maybe you know it, but even in the 1960s Forest Park 18 went through two different first holes. The second of them pretty well tracks one of the holes on Irwin's redesign, only in reverse. Before that, number one started east of there. A stream diagonally crossed the landing zone from left to right, then ran along the right side of the fairway to the green. I think some tennis courts are located there now.