PG 13.6 : Data corruption error message not being sent to syslog

This morning I noticed this error in my PG CSV log file.

```
2022-05-25 23:59:17.776 JST,,,117110,,628cf2c5.1c976,1,,2022-05-25 23:59:17 JST,9/611296,0,ERROR,XX001,"uncommitted xmin 16395356 from before xid cutoff 144683296 needs to be frozen",,,,,"while scanning block 19267 of relation ""relation_name""
```

This was a data corruption error that I resolved by truncating the table and reloading it. However, I was curious why this message was not sent to my syslog.

My logging configuration in the `postgresql.conf` is as follows:
```
# Logging settings
# ----------------
log_destination = 'csvlog,syslog'
logging_collector = on
log_directory = 'pg_log'
log_filename = 'postgresql_%Y%m%d.log'
log_truncate_on_rotation = off
log_rotation_age = 1h
log_rotation_size = 0

log_timezone = 'Japan'
log_line_prefix = '%t [%p]: [%l-1] %h:%u@%d:[PG]:CODE:%e '

log_statement = 'all'
log_min_messages = info         # DEBUG5
log_min_error_statement = info  # DEBUG5
log_error_verbosity = default
log_checkpoints = on
log_lock_waits = on
log_temp_files = 0
log_connections = on
log_disconnections = on
log_duration = off
log_min_duration_statement = 1000
log_autovacuum_min_duration = 3000ms
```

The OS info for the server on which this DB is running is as follows:
```
LSB Version:    :core-4.1-amd64:core-4.1-noarch
Distributor ID: CentOS
Description:    CentOS Linux release 7.9.2009 (Core)
Release:        7.9.2009
Codename:       Core
```

And there is a filter defined for the rsyslog messages as follows:
```
## Added by DataConsulting Team for syslog filter
if $programname == 'postgres' and \
($msg contains 'CODE:28000'    or \
$msg contains 'CODE:28P01'     or \
$msg contains 'CODE:3D000'     or \
$msg contains 'CODE:08006'     or \
$msg contains 'CODE:42501'        \
) then /xxxx/xxxx/xxx/pg_log/postgres_filter.log

if $programname == 'postgres' and \
(                                 \
not ($msg contains '[PG]') or \
$msg contains 'CODE:00000'     or \
$msg contains 'CODE:28000'     or \
$msg contains 'CODE:28P01'     or \
$msg contains 'CODE:3D000'     or \
$msg contains 'CODE:42501'     or \
$msg contains 'CODE:42601'     or \
$msg contains 'CODE:42P01'     or \
$msg contains 'CODE:42P02'     or \
$msg contains 'CODE:08006'     or \
$msg contains  'CODE:42703'       \
) then stop
```

`syslog_ident` and `syslog_facility` is as follows:
```
postgres=# show syslog_ident ;
 syslog_ident
--------------
 postgres
(1 row)

postgres=# show syslog_facility ;
 syslog_facility
-----------------
 local0
(1 row)
```

I was thinking that such an error message would be sent to the `/var/log/message`, from where it would be picked, but this wasn't the case. Could someone explain why this is so and what can I change for these messages to be sent to syslog?