Yes, the test case you described works as expected, but have you tried this:
- Start onionshare GUI - Add a file - Uncheck the "Stop server automatically" setting - Click "Start server" and wait for the server to come up - Download the file using Tor Browser - Select "New tor circuit for this site" in Tor Browser and try to download it again To me it seems that the GUI always shuts down the onion server after the first download regardles of the checkbox state.
