Isn't this kind of like branding? Ross' renovation work ran the gamut, from total re-routing and design to much less invasive work depending on the quality of the original course. Many of the courses mentioned in this thread should more accurately be labeled as Bendelow/Ross designs, however, the name Donald Ross became synonymous with quality, namely because his courses were hosting lots of major championships (professional & amateur) from the 1920's to present, while those of Tom Bendelow were not.
People recognized the Ross brand, and I think a lot of clubs where Ross worked in any capacity, grabbed onto the name over the years to associate themselves with a well-known master. The Ross name got slapped onto promotional material, scorecards, hats etc., and likely sold a few memberships along the way. A lot of it is probably attributable to marketing as opposed to actual accreditation.
TK