I saw that language. The way I read it, if boots are worn they must conform to the rule that lists prohibited items.
George Baylor wrote an article about Wild Bunch costuming that includes a photo of an army issued leather “walking shoe”. Not a boot, but legal under the general costuming language “typical of the late 19th and early 20th century”. See also the next sentence about “Edwardian period fashion” which would not be limited to boots.