i shall assume they got the date wrong then and they referred to the sabu version, as the sabu version was apparently 1940. , ruel's 1949 date of their post (and tom's spelling of thief) threw me off - there have been a number of versions
while sabu carried the kampilan upside down for a while (edge up), when he was actually using it, cutting at the spider, and later when he cut it's suspension thread, he held it correctly, striking with the edge, not the back of the blade, i looked carefully

he also carried it in his mouth edge out as he apparently didn't want to cut himself
the kampilan in the movie was similar to the above, which is edge down, and the angled fork of the grip up when held, tho some kampilans in modern repos have the angled fork also down, as below.
(images from google image search)