BUG #18934: Even with WITH ADMIN OPTION, I Cannot Manage Role Memberships

The following bug has been logged on the website:

Bug reference: 18934
Logged by: Luis Couto
Email address: snaperling(at)gmail(dot)com
PostgreSQL version: 16.8
Operating system: Windows 10
Description:

In PostgreSQL, I have a role hierarchy involving a user and two group roles:
Roles:
tester1(at)something — a user role (not superuser)
user_manager — an intermediate group role
user_group — the target group role whose membership I want to manage
| Role | Member Of | `WITH ADMIN
OPTION` |
| `tester1(at)something` | `user_manager` | YES
|
| `user_manager` | `user_group` | YES
|
In this configuration:
tester1(at)something should be able to add/remove members from user_group.
But it cannot — GRANT or REVOKE on user_group fails.
Even though tester1(at)something has full admin rights on user_manager, and
user_manager has admin rights on user_group.
Role Setup (After Manual Fix)
When I run:
REVOKE ADMIN OPTION FOR user_group FROM user_manager;
So that now:
Role Member Of WITH ADMIN OPTION
tester1(at)something user_manager YES
user_manager user_group NO
Now, unexpectedly:
tester1(at)something can add and remove members from user_group.
Even though no role in the chain has WITH ADMIN OPTION on user_group.
Summary of the Two Issues
1. Main Issue (Unexpected Restriction):
When user_manager has WITH ADMIN OPTION on user_group, and I (as
tester1(at)something) have WITH ADMIN OPTION on user_manager, I cannot manage
user_group.
This is confusing — PostgreSQL should allow it, as both admin links are
present. (maybe I'm getting something wrong)
2. Secondary Issue (Unexpected Permission Grant):
If I revoke admin option from user_manager on user_group, suddenly I can
manage user_group from tester1(at)something(dot)
This contradicts the documented need for WITH ADMIN OPTION and appears to
expose a privilege inconsistency or escalation.
What could be happening?
Thank you in advance,
Luis Couto