Comma separated list option for multiple value fields

I confirmed that the code provided does not work for multi-valued fields. In addition, the code didn't meet coding standards. Here's a modified version (which still doesn't solve the issue for multi-valued fields):

      // List format is a comma-separated list.
      if ($this->options['webform_element_format'] == 'list') {
        $result = [];
        $options['delta'] = 0;
        while ($formatted_item = $this->webformElementManager->invokeMethod('formatHtml',$composite_element, $webform_submission, $options)) {
          $result[] = $formatted_item['#plain_text'];
          $options['delta'] += 1;
        }

        return ['#markup' => implode(', ', $result)];
      }