Perhaps widget-essentials should not be a disable-able plugin?
If @psychobunny can't find a solution/workaround, that is.
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.