BUG #17049: what is the parameter wal_consistency_checking default value ?

The following bug has been logged on the website:

Bug reference: 17049
Logged by: yanliang lei
Email address: leiyanliang(at)highgo(dot)com
PostgreSQL version: 13.3
Operating system: CentOS7.6
Description:

in the document
https://www.postgresql.org/docs/current/runtime-config-developer.html
there is the following description about parameter
wal_consistency_checking：
The default value of this setting is the empty string, which disables the
feature

but in the following sql statement’s rusult，parameter
wal_consistency_checking default value is not empty string

postgres=# select * from pg_settings where
name='wal_consistency_checking';
-[ RECORD 1
]---+---------------------------------------------------------------------------------------------------------
name | wal_consistency_checking
setting |
unit |
category | Developer Options
short_desc | Sets the WAL resource managers for which WAL consistency
checks are done.
extra_desc | Full-page images will be logged for all data blocks and
cross-checked against the results of WAL replay.
context | superuser
vartype | string
source | default
min_val |
max_val |
enumvals |
boot_val |
reset_val |
sourcefile |
sourceline |
pending_restart | f

postgres=# select * from pg_settings where name='wal_consistency_checking'
and name='';
(0 rows) ---->>>this result returns zero rows

postgres=# select version();
-[ RECORD 1
]----------------------------------------------------------------------------------------------------
version | PostgreSQL 13.3 on x86_64-pc-linux-gnu, compiled by gcc (GCC)
4.8.5 20150623 (Red Hat 4.8.5-44), 64-bit

postgres=#

this problem also applies to PostgreSQL 14 Beta1 Version。