FormBuilder unset($element['#sorted']) won't sort it later

Please see drupal/core/lib/Drupal/Core/Form/FormBuilder.php:1038

    // If one of the child elements has a weight then we will need to sort
    // later.
    unset($element['#sorted']);

This is incorrect as the children in $element will never be sorted if it is used together with drupal/core/lib/Drupal/Core/Render/Element/Table.php:343

    foreach (Element::children($element[$first]) as $second) {
      // Assign the element by reference, so any potential changes to the
      // original element are taken over.
      $column = array('data' => &$element[$first][$second]);

      // Apply wrapper attributes of second-level elements as table cell
      // attributes.
      if (isset($element[$first][$second]['#wrapper_attributes'])) {
        $column += $element[$first][$second]['#wrapper_attributes'];
      }

      $row['data'][] = $column;
    }

See drupal/core/lib/Drupal/Core/Render/Element.php:72

    // Do not attempt to sort elements which have already been sorted.
    $sort = isset($elements['#sorted']) ? !$elements['#sorted'] : $sort;

This will always assigning $sort to FALSE.

Suggested fix is to replace unset($element['#sorted']); with $element['#sorted'] = FALSE;