init_file option does not allow changing passwords

This came up when resetting a forgotten password for a database user in mariadb 10.0.17, where typically the process was to restart with --init-file that applies some SQL like SET PASSWORD / UPDATE ... SET PASSWORD / GRANT ... IDENTIFIED BY. Under MariaDB 10.0.17 (and also tested under 10.1.3) this results in the following error in the error log and no effect:

ERROR: 1131 You are using MariaDB as an anonymous user and anonymous users are not allowed to modify user settings

This seems to only affect changing the password of existing users, but new users can be added with a password. Alternatively, skip-grant-tables can be used as an alternative (but we find less desirable) method to reset a password.

This seems like a bug, and fwiw, the behavior seems to differ from MySQL 5.6. Is this behavior of init-file in MariaDB intended?