Fwd: Why does pg_rewind deny permission for pg_read_binary_file() other than 'dbname=postgres'?

BTW rewinder is another USER that I made for control variable:

$ pg_rewind -D /pgdata --source-server='host=172.17.1.2 port=5432
user=rewinder dbname=postgres connect_timeout=5'
pg_rewind: source and target cluster are on the same timeline
pg_rewind: no rewind required
$ pg_rewind -D /pgdata --source-server='host=172.17.1.2 port=5432
user=rewinder dbname=repmgr connect_timeout=5'
pg_rewind: error: could not fetch remote file "global/pg_control": ERROR:
permission denied for function pg_read_binary_file

---------- Forwarded message ---------
From: Zhaoxun Yan <yan(dot)zhaoxun(at)gmail(dot)com>
Date: Thu, Oct 12, 2023 at 4:44 PM
Subject: Why does pg_rewind deny permission for pg_read_binary_file() other
than 'dbname=postgres'?
To: Pgsql-admin <pgsql-admin(at)lists(dot)postgresql(dot)org>

Hi there!

I am using repmgr and I have to use the command repmgr node rejoin
--force-rewind under 'dbname=repmgr'. It always fail on using pg_rewind,
the error is like this:
pg_rewind: error: could not fetch remote file "global/pg_control": ERROR:
permission denied for function pg_read_binary_file

I look into pg_rewind, and found that for a rewind user defined like
https://www.postgresql.org/docs/16/app-pgrewind.html

It always encounters such a problem if database != postgres but functions
when 'dbname=postgres'

$ pg_rewind -D /pgdata --source-server='host=172.17.1.2 port=5432 user=rep
dbname=repmgr connect_timeout=5'
pg_rewind: error: could not fetch remote file "global/pg_control": ERROR:
permission denied for function pg_read_binary_file
$ pg_rewind -D /pgdata --source-server='host=172.17.1.2 port=5432 user=rep
dbname=postgres connect_timeout=5'
pg_rewind: source and target cluster are on the same timeline
pg_rewind: no rewind required

What is the problem with it?

BTW, below is what I have done to USER rewinder:

CREATE USER rewinder;
GRANT EXECUTE ON function pg_catalog.pg_ls_dir(text, boolean, boolean) TO
rewinder;
GRANT EXECUTE ON function pg_catalog.pg_stat_file(text, boolean) TO
rewinder;
GRANT EXECUTE ON function pg_catalog.pg_read_binary_file(text) TO rewinder;
GRANT EXECUTE ON function pg_catalog.pg_read_binary_file(text, bigint,
bigint, boolean) TO rewinder;

# below is irrelevant to postgresql's pg_rewind
GRANT ALL PRIVILEGES ON DATABASE repmgr TO rewinder;
GRANT ALL PRIVILEGES ON SCHEMA repmgr TO rewinder;
GRANT pg_read_all_stats TO rewinder;
GRANT ALL ON SCHEMA repmgr TO rewinder;
GRANT SELECT ON DATABASE repmgr TO rewinder;
GRANT SELECT ON ALL TABLES IN SCHEMA repmgr TO rewinder;
GRANT SELECT ON SCHEMA repmgr TO rewinder;