My first thought on the 1921 and 1928 Maps was that they displayed a bit of artistic license, and the inaccuracies in the Cypress routing were kind of a best guess. But the specificity of the routings of the remainder of the Cypress course and on the other courses noted makes me think the maps were reflective of what was on the ground, or what was planned. My guess is that both of these maps were prepared in connection with the onset of the residential development of the Monterey Peninsula.
One of the questions that arose on the other thread was if we could identify the actual date of the "1921 Map." It was suggested that the location of the 18th green at Pebble might be a clue, but the green was moved by Fowler around 1922 and we know the map is from a later date.
There are probably other clues to be found. I'm going to post the closeups from each course from the various maps side by side, which might assist in placing each map on the timeline.
How do you know for sure that the map is from later than 1921?
The routing of Pebble Beach [with the 18th as a par 4] is accurate to 1921.
Isn't it possible someone had already done a rough routing for Cypress Point at that time? If the land was earmarked for future golf, instead of future development, they would have tried to figure out what land to set aside. There were a few golf architects [or guys who wanted to be one] around the place by then, and of course land planning firms sometimes do golf routings on their own, though I think it's unlikely a land planner would have laid out 15-16-17 at Cypress Point without clear marching orders from the client.
Note that the Cypress Point routings on the 1921 and 1928 maps are not identical - they are quite different on the inland holes. The "1921" map is closer to the actual routing or its predecessor; the 1928 map shows the 5th as a par 3 into the middle of the course, the 6th playing from there to 5 green, the 9th where today's 8th is, and then only one hole coming back inland from there before it turns around and heads toward the ocean [presumably today's 9th and not today's 10th]. In other words, the 1928 map is far enough off to not give it too much credibility.
I'm also curious what the white paths are on the 1928 map that run through both Cypress and Pebble. Bridle paths? They clearly aren't roads.