pg_basebackup behavior on non-existent slot

Hallo,

I was just confronted with this behaviour described back in 2017, and 
the participants in the thread seem to consider it a bug.  But I'm 
running on version 13.  So, how did that discussion end?

My case:
@ pg_basebackup -h 192.168.1.131 -D $PWD/13/main -U repuser -v -P -S stream
Password:
pg_basebackup: initiating base backup, waiting for checkpoint to complete
pg_basebackup: checkpoint completed
pg_basebackup: write-ahead log start point: 23/4E000028 on timeline 1
pg_basebackup: starting background WAL receiver
pg_basebackup: error: could not send replication command 
"START_REPLICATION": ERROR:  replication slot "stream" does not exist
53790996/53790996 kB (100%), 2/2 tablespaces 

pg_basebackup: write-ahead log end point: 23/4E000138
pg_basebackup: waiting for background process to finish streaming ...
pg_basebackup: error: child process exited with exit code 1
pg_basebackup: removing data directory "/var/lib/postgresql/13/main"
pg_basebackup: changes to tablespace directories will not be undone

The old thread:
https://postgrespro.com/list/thread-id/2337189#CAMkU=1wSxYBNFY9TzuVh3=mDLr4BBsMct6wcViNMH+-6Xon4Uw@mail.gmail.com

Kind regards,

Gerard