When installing recently I found the "-A " option of the initdb command only accepts lowercase argument. For example "-A LDAP" is not valid and must be "-A ldap" otherwise the following error is returned: initdb: invalid authentication method "LDAP" for "local" connections
It may be worth adding a note to the above documentation that states all option values must be specified in lowercase.
The -A option will accept any of the option names that are specified in the documentation for pg_hba.conf
It just so happens that all of those names, at present, consist of all lower-case characters.
That matching is case-sensitive is not specifically stated but is the default unless otherwise stated.
The page could use a hyperlink/cross-reference to the pg_hba.conf documentation.
But we don't go out of our way anywhere else to be so explicit about this kind of requirement and don't see a point of making this instance an exception.