In fact when it was added I privatised all my media and then synced.
No media were uploaded
I then un-privatised some selected media in FTM
The program then advised that a sync was needed
It only uploaded the unprivatised media
I then privatised some media again and re synced and the previous privatised media was uploaded and synced
Media names were not changed
It seems to work very well and was one of the changes that finally convinced me that after 18 months of refining (hence the number of patches) that link and sync was ready for showtime and I now have my file full linked