Subcategories not contained withing parent category group

The faq-category-hide-answer.tpl.php template indents questions that belong to child categories, but it does not group them in the <div class="faq-category-group"> div of their parent. This makes it impossible to perform simple theme tasks the FAQ output with CSS, such as placing a bottom border beneath top-level categories and their children.

For example, this is what the template produces (irrelevant content removed for brevity):

<div class="faq">
  <!-- TOP LEVEL GROUP -->
  <div class="faq-category-group">      <!-- Bottom border on this element will not enclose sub-categories -->
    <div class="faq-qa-header">
      <h5 class="faq-header"> Top-Level Category </h5>        
    </div>
    <div class="faq-qa">
      <div class="faq-dl-hide-answer">
        <div class="faq-question faq-dt-hide-answer">
        </div>
        <div class="faq-answer faq-dd-hide-answer" style="display: none;">
        </div>
      </div>
    </div>
  </div>
  <!-- END OF TOP LEVEL GROUP -->
  <!-- SUB-CATEGORY GROUP -->
  <div class="faq-category-indent">
    <div class="faq-category-group">
      <div class="faq-qa-header">
        <h6 class="faq-header"> Sub-Category </h6>
      </div>
      <div class="faq-qa">
        <div class="faq-dl-hide-answer">
          <div class="faq-question faq-dt-hide-answer">
          </div>
          <div class="faq-answer faq-dd-hide-answer" style="display: none;">
          </div>
        </div>
      </div>
    </div>
  </div>
  <!-- END OF SUB-CATEGORY GROUP -->
</div>

But this is what one would expect:

<div class="faq">
  <!-- TOP-LEVEL GROUP -->
  <div class="faq-category-group">        <!-- Bottom border on this element would enclose sub-categories -->
    <div class="faq-qa-header">
      <h5 class="faq-header"> Top-Level Category </h5>
    </div>
    <div class="faq-qa">
      <div class="faq-dl-hide-answer">
        <div class="faq-question faq-dt-hide-answer">
        </div>
        <div class="faq-answer faq-dd-hide-answer" style="display: none;">
        </div>
      </div>
    </div>
    <!-- SUB-CATEGORY GROUP -->
    <div class="faq-category-indent">
      <div class="faq-category-group">
        <div class="faq-qa-header">
          <h6 class="faq-header"> Sub-Category </h6>
        </div>
        <div class="faq-qa">
          <div class="faq-dl-hide-answer">
            <div class="faq-question faq-dt-hide-answer">
            </div>
            <div class="faq-answer faq-dd-hide-answer" style="display: none;">
            </div>
          </div>
        </div>
      </div>
    </div>
    <!-- END OF SUB-CATEGORY GROUP -->
  </div>
  <!-- END OF TOP-LEVEL GROUP -->
</div>