BUG #7578: Not able to drop user if S/he has permission on tablespace

The following bug has been logged on the website:

Bug reference: 7578
Logged by: Nikolay
Email address: wheelly(at)gmail(dot)com
PostgreSQL version: 9.1.4
Operating system: Linux version 3.2.0-3-amd64 (Debian 3.2.21-3)
Description:

Hello,

The bug is similar to existing bug "BUG #6116: Not able to drop user if S/he
has permission on tablespace".
http://archives.postgresql.org/pgsql-bugs/2011-07/msg00110.php

You wrote to mr. "tushar" <tushar(dot)qa(at)gmail(dot)com>:
------------------------------------------------------------------------
The "DROP OWNED BY" command only drops objects that are owned by a
user. It doesn't revoke privileges that user has granted: those
aren't considered dropable objects. So technically speaking all of
those commands are working just as expected.
------------------------------------------------------------------------

But documentation say reversal thing
(http://www.postgresql.org/docs/9.1/static/sql-drop-owned.html):
------------------------------------------------------------------------
DROP OWNED drops all the objects in the current database that are owned by
one of the specified roles.
Any privileges granted to the given roles on objects in the current database
will also be revoked.
------------------------------------------------------------------------

Where is a bug in PostgreSQL or in documentation?

Thank you,
Nikolay.