Robert Thompson said:
"It is Malcolm's take that many of the great courses attributed to Morris were actually almost entirely redone by Simpson at varying points, whether the club's acknowledge it or not. He says written documentation from and to Morris shows that often he arrived at a "course" in the morning, staked it out and played it that afternoon (Dornoch is a case in point, Dr. Malcolm says.)
Anyway, Simpson did extensive work at Muirfield, Cruden Bay, Aberdeen, Lytham, Sunningdale and Ballybunion. Pretty impressive list, when you think about it. So why isn't Simpson generally listed among the greats? Clearly the courses he was involved are considered great...."
Robert;
If that is true that Simpson redid a number of Old Tom Morris's courses, that kind of thing is probably not at all unusual for courses that date back to Old Tom.
The reason an architect like Simpson may not get the credit he deserves in that case, is, in my opinion, because most everyone doesn't really make any distinction of who did what at courses like that. Old Tom obviously did "lay out" the course, as you mentioned, and if he did it in the manner you described above (in a day) he should probably just be credited with the basic original routing of the course.
What an architect such as Simpson may have done on courses like that is to come in later and add features to them, make them more interesting and perhaps great. I call something like that "designing up" a golf course that may have been fairly basic or even mundane.
Sometimes the "routing phase" and the "designing up" phase happen not exactly simultaneously which is true of a number of the very old courses. People either forget or never exactly realized who did what. And in most all cases of courses that evolved like this they really are so old that no plans exist of who did what primarily because no plans probably existed or were used in the first place.