Actually, I'm not seeing AutoSave work very reliably at all.
If AutoRestoreFiles is off when you start slick, then you open a file and modify it, it won't autosave.
If you enable AutoRestoreFiles, then open a file and modify it, it won't autosave.
If you restart slick with AutoRestoreFiles enabled, autosave now seems to work.
If ExitOnAutoSave is enabled, and autosave is working, it saves the files to their original location, ignoring the option to autosave to a separate folder.
I started looking at this because I wondered what would happen if AutoRestore is off, yet you have a file which should have been autosaved then slick was terminated. I would expect slick to restart and remember the changes to the file the next time you load the file - but I don't know if that works since autosaving isn't working at all in this case.
I also found that when "Save To" is set to "SameName" or "SameNameDiffExtension", that the AUtoSave Directory is disabled in options, yet this setting is used to autosave untitled files.