I created a new repository file and did 'fossil open' on a new empty code directory.  I did 'fossil ui' to get to the web page and found that I was logged in as my Unix login username.

I went to the setup page and created a new user with full privileges.  Then I went to the logout page and tried to log in as the new user.  No effect.  Still logged in as Unix user.

I went back to the logout page and hit the logout button.  No effect.  Still logged in as Unix user.