> The reason it gets to be like that is that normal grant and revoke
> operations don't make any effort to reset the ACL field to null if
> the end result of a series of operations chances to be equivalent
> to the default. However, for reasons of its own pg_dump has to
> compute the set of GRANT/REVOKE commands to issue to get from the
> default state to the object's current state --- and in this situation
> that list is empty. So no commands are issued, the ACL stays null, ...
>
> That's not a bug, just an implementation artifact.
Okay, thanks for the quick and detailed response.