As is

At the FAT disks annex uses ajusted unlocked branch. Files use double space: in the file tree and in the .git folder.

As I wonder

At such disks, with option annex.thin, annex uses only file tree for keeping content. Content of the files in the .git folder is wiped.

done, dup of other todo, and I don't know how to avoid the problem with git deleting the file. --Joey