Related: #9165, #9902
Introduced in [15620], previously user_login
field was used for comparison.
The parameter itself was added in [2632]. We should probably deprecate it in favor of exclude
(#9902).
Still, fixing it makes sense to me. The description refers to "the 'admin' user that is installed by default":
http://core.trac.wordpress.org/browser/tags/3.5.1/wp-includes/author-template.php#L246
Codex specifically refers to the login: "Exclude the 'admin' (login is admin) account from the list":
http://codex.wordpress.org/Function_Reference/wp_list_authors#Parameters
The default username, however, can be manually picked now (#10396).
I guess we have the following options to fix this:
'admin' == $author->user_login
.
1 == $author->ID
(from #9165).
get_option('admin_email') == $author->user_email
(from comment:1).