PG 10 streaming replication pg_wal question

Hi LIst,
I am testing PG10 streaming replication , with archiving off, I have
pg_wal on separate directory to monitor the growth , I had the slave
offline yesterday for more than 20h while I was restoring one of db
(60GB) with pg_restore from a backup taken with pg_dump, today I brought
the slave PG host online and replication catch up nicely , master and
slave are in sync now, but on master host the pg_wal is still same
large size ( as yesterday) even after all the wal files had been
applied to salve, would replication process not suppose to removed the
wal files on master after being applied to salve ?
( do I need to manually implement a cleanup job of this wal files, as
mentioned archiving is off on both servers)
see bellow:

master: pg_current_wal_lsn
--------------------
C5/D82DDD68

and slave: pg_last_wal_receive_lsn
-------------------------
C5/D82DDD68

and master :
4.0K ./wal/archive_status
166G ./wal
last wal file :
w------- 1 postgres postgres 16777216 Nov 29 16:05 00000007000000C5000000D8

ans slave :
12K ./wal/archive_status
1.1G ./wal

last wal file:
rw------- 1 postgres postgres 16777216 Nov 30 08:56 00000007000000C5000000D8