I think a lot has to do with Scott not wanting to go down a rabbit hole and add many pages to a catalog. If you add 2500 listings for these stamps what about other Countries. Pretty soon you have a 12-volume set with a whole lot of listings that nobody will ever care about.
Quote:
The majority of printings were line-perforated 12½ and 9¼, but you can also find examples perforated 5¼, 6½, 10½, 11½ and 13½, and stamps which are imperforate. And that's not all. There are also compound perfs to be found, where a stamp has two or even three of the different types.
Add up all these permutations, you will need to find almost 2,500 varieties to complete a collection of all possible types of all values! Needless to say, it is thought that no-one has yet managed to do this!
https://www.stampmagazine.co.uk/bos...found%20used.