Tom,
Myths also grow from facts - the courses steeped in mythology are often connected to historic events like big tournaments. And with greater interest in gca, as well as a seemingly ever increasing fascination with brands, a course's image (equated with myth for this discussion) is enhanced by a connection with a Golden Age gca.
Also, I think Mike is crediting the superintendents with improving maintenance conditions to the forefront of courses in whatever era - those tourney courses are usually among the best maintained then and now, which increases their image, and the minor changes that we may not be aware of, as in your Raynor examples.
Greens on almost any course have certainly been resurfaced, and probably slightly recontoured, if for nothing else because of green speed, but maybe to take out "unfair humps" or whatever that members complained about. Similarly, bunkers have been rebuilt, and in the process, pulling them out or back just a few feet might change the playability of the course. For that matter, landscape tree planting and growth affects design and ambiance for most people, even if a single feature is never touched.
Short version - courses change after the gca leaves, and after the gca dies, often in subtle ways that better them, even if we focus on the ones that don't on this site.
Is that too much of a generalization for you to accept?