That's what their website says, however I had a play and created a file and logged in and out and the file persisted as did my ability to look at the /onion directory via Tor after the ssh session was stopped.
Your home directory is in /sec/root.
If you install tools outside of /sec/usr they will be reset on your next visit. So if you want to install something that survives a session log out you need to install to /sec/usr