The thing I am keying in on is that it’s only the extensions that have underscores in them. I hadn’t seen any file extensions like that before KiCad, but it’s a large part of the file extensions that are part of the software. The board files have an extension of “.kicad_pcb” and the footprint files are “kicad_mod”.
I have all of the files listed in the “authorized extensions”, as well as the asterisk, in hopes of getting this working. I tried searching through the git repo as well, but couldn’t find any restrictions on the extension type (though it doesn’t mean that’s not the case).