rwmb_frontend_validate and user_login

Hi

is it possible to target the user_name/user_login inside the rwmb_frontend_validate filter?

public function userRegisterFormValidation() {

add_filter( 'rwmb_frontend_validate', function( $validate, $config ) {
    if ( 'dc-user' !== $config['id'] ) {
        return $validate;
    }
    if ( $_POST['user_login'] == 'example' ) {
        $validate = 'custom message'; 
    }
    return $validate;
}, 10, 2 );
}