What I also learnt was that if there already are saves with same name (autosaves) then they will be overwritten by whatever steam version gets launched last with no warning.
So, my scenario was that I installed Steam to my Linux partition and I thought I copied over the saves/mods dir from Windows. I messed up a little and instead copied over saves from an ancient version of factorio somehow (earliest autosave was dated to January 2014

I know I can disable cloud sync completely but I was wondering if it was somehow possible to check if existing saves with same name are newer/older/different and allow the user to pick if they want to upload/overwrite them.