I tested a few mp3 files on my Clip Sport before completing this reply.
For several mp3 files I copied into the “Audiobooks” folder and into the “Podcasts” folder (under the root folder) of my Clip Sport, the device created one unique “pos” resume file for each mp3 file I played. I did not experience any loss of the resume capability for all the files when I jumped back and forth between multiple files.
(I used Win File Explorer to verify the creation of multiple “pos” files in each subdirectory)
I am currently using FW 1.28 (but likely the same capability exists in FW 1.27