Ran can correct me I'm wrong, but I don't think he is trying to identify the 147 best courses. He leaves out lots of courses that are likely sure things for such a list. Some examples include Pine Valley, CPC, Shinnie, Oakmont, ANGC and Tara Iti.
A number of years ago, GCA did an unofficial world rating of courses. Any GCA members could rate any course they chose, using their interpretation of the Doak scale. The results were tabulated and posted. It struck me how many courses in the GCA top 100 were also in the GD and GM top 100s. The order differed somewhat, and there were a few outliers. But most of our courses were on the mag lists, and vice versa.