missing client_hostname

I have postgres 12 running in centos7.

I recently have configured streaming replication from master to standby using below command:

/usr/bin/pg_basebackup -h <master ip> -p 5432 -U replication -D /path/of/data/directory/ -Fp -R -Xs -P -c fast

It was successfully configured but when I query pg_stat_replication I don't get the hostname in output:

postgres=# select * from pg_stat_Replication;
-[ RECORD 1 ]----+------------------------------
pid              | 3692075
usesysid         | 16384
usename          | replication
application_name | walreceiver
client_addr      | slave_ip

client_hostname  |
client_port      | 52500
backend_start    | 2023-11-01 08:26:45.373297-07
backend_xmin     |
state            | streaming
sent_lsn         | 2E5/400001C0
write_lsn        | 2E5/400001C0
flush_lsn        | 2E5/400001C0
replay_lsn       | 2E5/400001C0
write_lag        |
flush_lag        |
replay_lag       |
sync_priority    | 0
sync_state       | async
reply_time       | 2023-11-01 08:41:47.60122-07

So please help me understand the reason for this and how I will fix this issue of having a respective hostname in this catalog.

Regards,

Atul