If your question is still:
"CREATE ONE (OR MORE) NONEXISTENT DIRECTORIES a completely different task?"
In order to manage my folders, I use those lines in the relevant case:
Create all the folders from "a" to "e". If folder "a" already exists then from "b" to "e".
etc...
set mkdirFolder to "mkdir -p " & desktopPath & "a/b/c/d/e/"
do shell script mkdirFolder
Create a folder "a" if not exists and folders "b to e" at his top-level
set mkdirFolder to "mkdir -p " & desktopPath & "a/{b,c,d,e}/"
do shell script mkdirFolder
Create folder with a part of the name
-- (Note the single quotes round the space to mark it as part of the name.)
set mkdirFolder to "mkdir -p " & desktopPath & "a/Chapter' '{1,2,3,4}/"
do shell script mkdirFolder
result--> Folders "Chapter 1", "Chapter 2", "Chapter 3", and "Chapter 4" are created in folder "a"
You can find more informations here (Learn more about creating folder with "mkdir")