truncate table restart identity for non-owner

Hi,

It's currently impossible for a non-owner user to do 'TRUNCATE table
RESTART IDENTITY;' even with ALL privileges on both the table and the
sequences because of the implied ALTER SEQUENCE RESTART operation.

Why does it work that way instead of using 'SELECT setval('foo', 1,
false);' which is equivalent and allowed for users with UPDATE privilege?

Bastien