Feeding it into DBinfo I can see the appended playlist files (appended with .1, .2, .3 and so on) call the same numbered stream files with no appended .1, .2, .3
If I had to guess the uploader may have uploaded the content of all six disk, and appended numbers to context that was different between the 6 to save on uploading the same file more then once?
Where I am getting stuck in this logic is why there are 12 index files in the upload while there should only be 6 disks as listed in the .XML files.
From what I can tell makemkv can only handel reading one index file at a time.