Good mention. When I arrived on Monday, even after a ten-year absence, the rocks jumped at me. They are quite fetching. I don't know the rationale for their placement.
If I had to venture a guess, I suspect that the Oak Hill movers would say something along these lines: "The West course is our Donald Ross layout and always shall be. The East course is our tournament venue and, come hell or high Allen's-Creek water, we will make whatever changes the current administration feels are necessary to attract first-class tournaments."
So, if the PGA is looking for one thing, the USGA something else, they'll oblige. I wouldn't be surprised to see a USGA Senior Open at Oak Hill, as a test of the course and membership to host another US Open in the 2020s or 2030s.