What you are selecting are the global privileges.
You are however giving database (and host, but that doesn’t matter) specific privileges.
GRANT INSERT ON wordpress.* TO 'www'@'localhost' IDENTIFIED BY 'basic';
These permissions are stored in the db table.
Just to point you in the right direction:
SHOW GRANTS FOR 'www'@'localhost'
http://dev.mysql.com/doc/refman/5.0/en/show-grants.html