Tom Mac,
Based on courses I have seen, I always considered Muirfield the first "modern" course, in that greens, tees, bunkers and routing all had sizes, locations, etc. we would consider normal today. I also feel that by the 1920's, American designers had pretty well figured out and adapted designs to American conditions, and that we follow those principals today.
The exceptions are the big budget courses of the last 20 years, where technology and economy have allowed designers to explore different paradigms, like moving lots of earth to create a special look (ie Whistling Straights, Shadow Creek) although, you could point to Lido to say that even that is not new. Other than that, economy generally still rules the day, and leads architects to find convenient fill sources, like Ross.
I also feel, that as a rule in the Golden Age, the designers learned from each other, and as they went. As has been noted, these designer seemed more likely to collaborate, and I feel it is because they were all feeling their way. I think it led to the formation of ASGCA, and I think it is still going on today, in different forms.
So, Ross, was not, IMHO, advanced for his time. As a group, the Golden Age designers truly advanced the profession and philosophy of golf course design. As probably the most national of the prominent architects, he may have made some headway first in adapting designs to different climates across the US. An example is his work in grassing the greens at Pinehurst.
Over his career, other technology, like irrigation, earthmoving and drainage all evolved signifigantly. I have seen the Northland CC plans, and a local engineer did the rudimentary irrigation system. I imagine Ross had to see and learn how these "new technologies" would affect his design. Who knows, he may have felt irrigation was unnecessary in that climate, (Having built three courses in that region, I still question that today!)
I also recall that at Seminole, he altered his traditional bunker style, which I have always felt was a REACTION to losing ANGC to MacKenzie and his more flamboyant style. So, in these two cases, Ross was simply "middle of the pack" in style and engineering, if not in number of courses built.
As to visibility, Ross writes it was important, and we can only imagine that he was reacting to "Alps" style holes. I think he tried for visibility, but accepted it was not always possible, especially in the Rock of New England. When he found silt and clay in Detroit that could be cut as far as he wanted, he went for it! I think he would be satisfied to see the flag, and my opinion is that seeing the base of the flag was a discussion item in his career, but not mandatory until the big money tour of the 1960's evolved.
I understand some of my post is speculation, but you asked for my opinions.
I hope I don't offend any one with this post.