...
protected function order(){

    add_filter('acf/validate_save_post', function(){


        if(!isset($_POST['acf']['field_65067bd15086d'])) return;

        $email = $_POST['acf']['field_65067bd15086d']['field_65067bde5086e'];
        $confirmEmail = $_POST['acf']['field_65067bd15086d']['field_65067e4f26db1'];


        if(
            !filter_var($email, FILTER_VALIDATE_EMAIL)

            ||

            $email !== $confirmEmail
        ){

            acf_add_validation_error('acf-field_65067bd15086d-field_65067bde5086e', 'ok');

        }

    });

}
...