I had the same problem, but you can find and use these files. These work fine, but there is no instruction for locating them. Open the file manager and go to "/usr/share/doc/synfig-examples/examples"... right click a file and choose "open with/other application"... Scroll down and choose Synfig from the list, then left click the "Set as default" button. Now every time you double-click one of these file types it will open in Synfig. This is probably one of several options.
can' t open the examples