BUG #16795: Can't give "grant execute on pg_start_backup to .." - Mailing list pgsql-bugs

The following bug has been logged on the website:

Bug reference:      16795
Logged by:          Ken
Email address:      ken.karma@gmail.com
PostgreSQL version: 13.1
Operating system:   CentOS Linux release 7.9.2009
Description:

I'm want to make backup user who haven't SUPERUSER, but have "Replication"
role what must be enough, in document:
25.3.3.1. Making a Non-Exclusive Low-Level Backup
A non-exclusive low level backup is one that allows other concurrent backups
to be running (both those started using the same backup API and those
started using pg_basebackup).
    Ensure that WAL archiving is enabled and working.
    Connect to the server (it does not matter which database) as a user with
rights to run pg_start_backup (superuser, or a user who has been granted
EXECUTE on the function) and issue the command:
    SELECT pg_start_backup('label', false, false);
But I can't give this grant:
 psql -U postgres
psql (13.1)
Type "help" for help.
postgres=# create role backup replication login;
CREATE ROLE
postgres=# grant pg_read_all_settings to backup ;
GRANT ROLE
postgres=# grant SELECT on pg_start_backup to backup ;
ERROR:  relation "pg_start_backup" does not exist
postgres=# grant EXECUTE on pg_catalog.pg_start_backup to backup ;
ERROR:  relation "pg_catalog.pg_start_backup" does not exist
postgres=# grant SELECT on pg_catalog.pg_start_backup to backup ;
ERROR:  relation "pg_catalog.pg_start_backup" does not exist
postgres=# select pg_start_backup('Daily backup');
 pg_start_backup
-----------------
 0/10000028
(1 row)
postgres=# \df pg_start_backup ;
                                                        List of functions
   Schema   |      Name       | Result data type |
Argument data types                           | Type

------------+-----------------+------------------+------------------------------------------------------------------------+------
 pg_catalog | pg_start_backup | pg_lsn           | label text, fast boolean
DEFAULT false, exclusive boolean DEFAULT true | func
(1 row)


[root@host.test.mta ~]# psql -U backup postgres
psql (13.1)
Type "help" for help.

postgres=> select pg_start_backup('Daily backup');
ERROR:  permission denied for function pg_start_backup

postgres=> \du+
                                                 List of roles
 Role name |                         Attributes                         |
   Member of        | Description
-----------+------------------------------------------------------------+------------------------+-------------
 backup | Replication                                                |
{pg_read_all_settings} |
 postgres  | Superuser, Create role, Create DB, Replication, Bypass RLS | {}
                    |

In PostrgreSQL log:
2020-12-28 19:20:07.696 EET postgres postgres [10076]ERROR:  relation
"pg_catalog.pg_start_backup" does not exist
2020-12-28 19:20:07.696 EET postgres postgres [10076]STATEMENT:  grant
EXECUTE on pg_catalog.pg_start_backup to backup ;
2020-12-28 19:21:48.853 EET postgres postgres [10076]ERROR:  relation
"pg_catalog.pg_start_backup" does not exist
2020-12-28 19:21:48.853 EET postgres postgres [10076]STATEMENT:  grant
SELECT on pg_catalog.pg_start_backup to backup ;
2020-12-28 20:18:30.281 EET postgres backup [12482]ERROR:  permission denied
for function pg_start_backup
2020-12-28 20:18:30.281 EET postgres backup [12482]STATEMENT:  select
pg_start_backup('Daily backup');

Do I miss something, why can't I give execute on pg_start_backup to user
backup?