BUG #11350: ALTER SYSTEM is not DDL?

The following bug has been logged on the website:

Bug reference:      11350
Logged by:          Tomonari Katsumata
Email address:      katsumata.tomonari@po.ntts.co.jp
PostgreSQL version: 9.4beta2
Operating system:   RHEL6.4 x86_64
Description:

Hi,

I found an odd thing about logging for alter system.

When I set 'log_statement=ddl' and execute ALTER SYSTEM,
any log messages are not outputted.

-----------------------------------------------
[log_statement = ddl]
postgres=# alter system set autovacuum to off;
ALTER SYSTEM
-----------------------------------------------

Whereas, when I set 'log_statemnt = all' then log messege is outputted.

-----------------------------------------------
[log_statement = all]
postgres=# alter system set autovacuum to off;
LOG:  statement: alter system set autovacuum to off;
ALTER SYSTEM
-----------------------------------------------

The document says about log_statement:
>ddl logs all data definition statements, such as CREATE, ALTER, and DROP
statements.

So I think log message should be outputted when executing ALTER SYSTEM with
'log_statement = ddl'.

Am I missing something?