Is this still an issue? I have just noticed that non of the sidebar widgets display to anon users.
Edit- nvm i think it is a theme issue.
Happens here and on my own forum too, nodebb stats says 12 online, but I'm seeing 12 signed in users (online), 1 marked as away and 21 guests. Unless this has been tweaked to only show those with the online status, and not the number of users currently viewing.
Nice catch fixed in widget essentials, it was only displaying registered users.