--protocol option of mysql client program confuses me

[aaron chan]

"The --protocol option enables you to establish a particular type of connection even when the other options would normally default to some other protocol."
the explanation makes me think the --protocol option has a high priority and it decides which protocol to use and it will pick up other necessary corresponding options and ignore irrelevant options to make a connection.
However,the error below confuses me:
[root@ansible2 ~]# mysql --no-defaults-file -uroot -p8Lv1Dnfc@ --host=10.82.12.69 --socket=/app/mysql/3306/socket/mysql.sock --protocol=socket
mysql: [Warning] Using a password on the command line interface can be insecure.
ERROR 2047 (HY000): Wrong or unknown protocol

here,i specify the protocol to be "socket",and the socket file path is right,but ERROR 2047 happens. why does not ignore the "--host" option automatically?