pg_basebackup in tar format with -Xs

The following documentation comment has been logged on the website:

Page: https://www.postgresql.org/docs/9.6/app-pgbasebackup.html
Description:

Only since Postgres 10, one can take backup of wals along with full backup
(in tar format) using pg_basebackup

ERROR:
pg_basebackup: WAL streaming can only be used in plain mode
Try "pg_basebackup --help" for more information

You dont see that error since Postgres 10 instead you see a separate tar
file for wals.