You need to actually revoke something to make the point stand out.

postgres=# \z tt1
                              Access privileges
 Schema | Name | Type  |   Access privileges   | Column privileges | Policies
--------+------+-------+-----------------------+-------------------+----------
 public | tt1  | table | davidj=arwdDxt/davidj |                   |
(1 row)
postgres=# revoke update on tt1 from davidj;
REVOKE
postgres=# \z tt1
                              Access privileges
 Schema | Name | Type  |  Access privileges   | Column privileges | Policies
--------+------+-------+----------------------+-------------------+----------
 public | tt1  | table | davidj=ardDxt/davidj |                   |
(1 row)

postgres=# alter table tt1 owner to testowner;
ALTER TABLE
postgres=# \z tt1
                                 Access privileges
 Schema | Name | Type  |     Access privileges      | Column privileges | Policies
--------+------+-------+----------------------------+-------------------+----------
 public | tt1  | table | testowner=ardDxt/testowner |                   |
(1 row)

The new owner, testowner, is missing the same update privilege that davidj removed from himself.  In short, setting owner does indeed cause explicit grants to appear in the system, grants that can be revoked.  And so, yes, transferring ownership transfers the set of grants currently in effect for the existing owner.

I can see making this detail more clear in the DDL chapter.  It is unrelated to the confusion behind the topic of this thread though.

David J.

Hello again,

note that my point concerns "alter database" not "alter table".

See my last reply for an example

Regards