Dear Peter,
> Note that the latter includes pg_basebackup, pg_receivewal, and
> pg_recvlogical, which feel generally similar to pg_createsubscriber.
Hmm, but similar command pg_upgrade was included in the server app page.
The page [1] defined that server commands are the command can be run on the same
server with the postgres server process. IIRC, the command was categorized as
"Server Application" because it assumed standby is running on the same machine.
But... I think the command is located on the border between the server and the client.
We should hear other opinions too.
[1]: https://www.postgresql.org/docs/devel/reference-server.html
Best regards,
Hayato Kuroda
FUJITSU LIMITED