I will not claim to be an expert relative to many of the people here. I have also never been to Cypress Point and am not great at reading a topo map yet. So someone please correct me if I made any mistakes.
I was surprised that in the interesting podcast nobody talked about what Mackenzie's routing "fingerprints" are and whether any of the changes between the versions has have his fingerprints on them. I have readthat Mackenzie is known for repeatedly using an interesting landform as a "focal point" of his routings, which repeatedly use and return to the focal point landform. Think the hill near 7 green at Augusta.
I recall reading that the way Mackenzie used a prominent sand dune at Cypress is a prime example of one of his focal points. It is behind 6 and 11 greens (and near 3 green), houses the tee for 7, 10, and 12, and the green for 9. Others have said that this feature of the routing is what screams Mackenzie's name at Cypress. The Golf Digest "Every Hole at Cypress Point" video makes this dune's prominence and usage on each hole very clear.
Given this, it is interesting to notice that the use of the dune is very different in the 1921 relative to the 1924 maps. In particular, the 1924 map looks much more like a Mackenzie routing. The dune is not as clear in the topo lines on the 1921 map, but it looks like the 10th hole (a par 3 or short par 4?) is played over the dune and the 11th tee is playing off of it. That dune is not used repeatedly as a focal point of the routing. But in the 1924 routing, you can see the short par 4 9th played into a green set on the dune, the 10th played off the dune, the 11th played to a green set into the dune, and the 12th played back off of it. The 3rd green is also moved towards the base of it relative to the 1921 map. The main difference between the 1924 map and Cypress as built is that the course uses that dune even more than the 1924 map, as the dune backs the 6th green and is used for the teeing ground for the par 3 7th which plays to the east. It thus seems to me that the use of that dune in the 1924 maps has the hallmarks of a Mackenzie routing while the 1921 map does not.
Curious what people think of this observation.