In the smb.conf(5) man page, the description for the "allow trusted domains" say the following : "This option only takes effect when the security option is set to server or domain." From my limited testing, it also appear to take effect when "security = ads". It might be worth to rephrase the description to include it.
Thanks. The man page entry has been updated.
sorry for the same, cleaning up the database to prevent unecessary reopens of bugs.