Trouble with v16 new CREATEROLE semantic

Typically, each "instance" of our app lives in its own DB, and uses a naming convention for its ROLEs, to make those role names unique per-app-instance. All the app roles are created by a single master role (the "owner" role), with CREATEROLE, and that master role also owns all the schemas (of that app's instance, also using a (schema) naming convention similar to the role's one, despite schemas not being cluster-wide like roles).

We started this on v12. No problem with v14. But with v16, we're running into trouble...

So I've tried to replicate our setup in a single demo, on both v14 and v16.

with V14.8 ===============================

ddevienne=> select roleid::regrole::text, member::regrole::text, admin_option from pg_auth_members where roleid::regrole::text like 'z%' or member::regrole::text like 'z%';
 roleid | member | admin_option
--------+--------+--------------
(0 rows)
ddevienne=> create role zowner nologin createrole; -- owner of app's schemas and manager of related roles
CREATE ROLE
ddevienne=> select roleid::regrole::text, member::regrole::text, grantor::regrole::text, admin_option from pg_auth_members where roleid::regrole::text like 'z%' or member::regrole::text like 'z%';
 roleid | member | grantor | admin_option
--------+--------+---------+--------------
(0 rows)
ddevienne=> grant zowner to ddevienne;
GRANT ROLE
ddevienne=> select roleid::regrole::text, member::regrole::text, grantor::regrole::text, admin_option from pg_auth_members where roleid::regrole::text like 'z%' or member::regrole::text like 'z%';
 roleid |  member   |  grantor  | admin_option
--------+-----------+-----------+--------------
 zowner | ddevienne | ddevienne | f
(1 row)
ddevienne=> set role zowner;
SET
ddevienne=> create role zadmin nologin noinherit in role zowner; -- means to become zowner explicitly
CREATE ROLE
ddevienne=> create role zuser nologin; -- has grants on zowner's schemas
CREATE ROLE
ddevienne=> create role zuser_a in role zuser;
CREATE ROLE
ddevienne=> create role zuser_b in role zuser, zadmin;
CREATE ROLE
ddevienne=> select roleid::regrole::text, member::regrole::text, grantor::regrole::text, admin_option from pg_auth_members where roleid::regrole::text like 'z%' or member::regrole::text like 'z%';
 roleid |  member   |  grantor  | admin_option
--------+-----------+-----------+--------------
 zowner | ddevienne | ddevienne | f
 zowner | zadmin    | zowner    | f
 zuser  | zuser_a   | zowner    | f
 zuser  | zuser_b   | zowner    | f
 zadmin | zuser_b   | zowner    | f
(5 rows)

And now with V16.1 ===========================

ddevienne=> select roleid::regrole::text, member::regrole::text, grantor::regrole::text, admin_option from pg_auth_members where roleid::regrole::text like 'z%' or member::regrole::text like 'z%';
 roleid | member | grantor | admin_option
--------+--------+---------+--------------
(0 rows)
ddevienne=> create role zowner nologin createrole; -- owner of app's schemas and manager of related roles
CREATE ROLE
ddevienne=> select roleid::regrole::text, member::regrole::text, grantor::regrole::text, admin_option from pg_auth_members where roleid::regrole::text like 'z%' or member::regrole::text like 'z%';
 roleid |  member   | grantor  | admin_option
--------+-----------+----------+--------------
 zowner | ddevienne | postgres | t
(1 row)
ddevienne=> set role zowner;
ERROR:  permission denied to set role "zowner"
ddevienne=> select roleid::regrole::text, member::regrole::text, grantor::regrole::text, admin_option, set_option, inherit_option from pg_auth_members where roleid::regrole::text like 'z%' or member::regrole::text like 'z%';
 roleid |  member   | grantor  | admin_option | set_option | inherit_option
--------+-----------+----------+--------------+------------+----------------
 zowner | ddevienne | postgres | t            | f          | f
(1 row)
ddevienne=> grant zowner to ddevienne;
GRANT ROLE
ddevienne=> select roleid::regrole::text, member::regrole::text, grantor::regrole::text, admin_option, set_option, inherit_option from pg_auth_members where roleid::regrole::text like 'z%' or member::regrole::text like 'z%';
 roleid |  member   |  grantor  | admin_option | set_option | inherit_option
--------+-----------+-----------+--------------+------------+----------------
 zowner | ddevienne | postgres  | t            | f          | f
 zowner | ddevienne | ddevienne | f            | t          | t
(2 rows)
ddevienne=> set role zowner;
SET
ddevienne=> create role zadmin nologin noinherit in role zowner; -- means to become zowner explicitly
ERROR:  permission denied to grant role "zowner"
DETAIL:  Only roles with the ADMIN option on role "zowner" may grant this role.
ddevienne=>

So first surprise in V16. Despite having admin_option, from being the creator of the zowner role, I can't SET ROLE to it. I have to explicitly add the SET privilege.

And then, when ddevienne SET ROLE's to zowner, and tries to create zadmin *and* add it at the same time as a member of zowner (the current_role), it fails.

So it looks like, despite ddevienne having admin_option on zowner, because it is on a "different line" than the set_option, it still cannot add members in zowner???

I find that surprising. What's going on here?

When I read about v16, I thought great, this fits our intent, a single "owner" ROLE with CREATEROLE which is limited to administering only the ROLEs it created itself. I've always been bothered by the mega-power of CREATEROLE. But now that we're actually trying to use it, I'm a bit worried. Can someone explain (or guess) what I'm missing here?

Thanks, --DD