Comment 11 for bug 1074807

Because auth_admin has absolutely nothing to do with sudo but with the fact that you would have to authenticate as admin (i.e. the account that makes the request needs to be in an adminesque group such as 'admin' and the user needs to authenticate as being the owner of the account by means of passphrase).

^

AdminIdentities does exactly what I wrote there, specify which groups and/or accounts are considered an admin. If the requester is not part of the AdminIdentities they are not getting in, if they fail to provide the password for the account they are also not getting in. And it still has no other relation to sudo other than ubuntu having a group sudo which is qualifying as adminesque.