diff -u b/core/includes/form.inc b/core/includes/form.inc
--- b/core/includes/form.inc
+++ b/core/includes/form.inc
@@ -312,7 +312,6 @@
 
   $variables['legend']['title'] = (isset($element['#title']) && $element['#title'] !== '') ? Xss::filterAdmin($element['#title']) : '';
   $variables['legend']['attributes'] = new Attribute();
-
   $variables['legend_span']['attributes'] = new Attribute();
 
   if (!empty($element['#description'])) {
@@ -324,11 +323,6 @@
     // Add the description's id to the fieldset aria attributes.
     $variables['attributes']['aria-describedby'] = $description_id;
   }
-
-  // Pass element's #type to template.
-  if (!empty($element['#type'])) {
-    $variables['type'] = $element['#type'];
-  }
 }
 
 /**
@@ -551,7 +545,7 @@
     $variables['attributes']['id'] = $element['#id'];
   }
 
-  // Pass element's #type and #name to template.
+  // Pass elements #type and #name to template.
   if (!empty($element['#type'])) {
     $variables['type'] = $element['#type'];
   }
@@ -559,7 +553,7 @@
     $variables['name'] = $element['#name'];
   }
 
-  // Pass element's disabled status to template.
+  // Pass elements disabled status to template.
   $variables['disabled'] = !empty($element['#attributes']['disabled']) ? $element['#attributes']['disabled'] : NULL;
 
   // If #title is not set, we don't display any label.
@@ -618,7 +612,7 @@
   $variables['title'] = (isset($element['#title']) && $element['#title'] !== '') ? Xss::filterAdmin($element['#title']) : '';
   $variables['attributes'] = array();
 
-  // Pass element's title_display to template.
+  // Pass elements title_display to template.
   $variables['title_display'] = $element['#title_display'];
 
   // A #for property of a dedicated #type 'label' element as precedence.
@@ -635,7 +629,7 @@
     $variables['attributes']['for'] = $element['#id'];
   }
 
-  // Pass element's required to template.
+  // Pass elements required to template.
   $variables['required'] = !empty($element['#required']) ? $element['#required'] : NULL;
 }
 
reverted:
--- b/core/lib/Drupal/Core/Render/Element/CompositeFormElementTrait.php
+++ a/core/lib/Drupal/Core/Render/Element/CompositeFormElementTrait.php
@@ -33,6 +33,8 @@
     if (isset($element['#title']) || isset($element['#description'])) {
       // @see #type 'fieldgroup'
       $element['#theme_wrappers'][] = 'fieldset';
+      $element['#attributes']['class'][] = 'fieldgroup';
+      $element['#attributes']['class'][] = 'form-composite';
     }
     return $element;
   }
diff -u b/core/modules/system/templates/fieldset.html.twig b/core/modules/system/templates/fieldset.html.twig
--- b/core/modules/system/templates/fieldset.html.twig
+++ b/core/modules/system/templates/fieldset.html.twig
@@ -7,7 +7,6 @@
  * - attributes: HTML attributes for the fieldset element.
  * - required: The required marker or empty if the associated fieldset is
  *   not required.
- * - type: The type of the element.
  * - legend: The legend element containing the following properties:
  *   - title: Title of the fieldset, intended for use as the text of the legend.
  *   - attributes: HTML attributes to apply to the legend.
@@ -23,21 +22,7 @@
  * @ingroup themeable
  */
 #}
-{% if type in ['radios', 'checkboxes'] %}
-   {%
-     set composite_element_classes = [
-        'fieldgroup',
-        'form-composite',
-      ]
-   %}
-{% endif %}
-<fieldset{{ attributes.addClass('form-item', 'form-wrapper', composite_element_classes) }}>
-  {% if legend.title is not empty or required -%}
-    {%
-      set legend_classes = [
-        title_display == 'invisible' ? 'visually-hidden',
-      ]
-    %}
+<fieldset{{ attributes.addClass('form-item', 'form-wrapper') }}>
     {%
       set legend_span_classes = [
         'fieldset-legend',
@@ -45,7 +30,7 @@
       ]
     %}
     {#  Always wrap fieldset legends in a SPAN for CSS positioning. #}
-    <legend{{ legend.attributes.addClass(legend_classes) }}>
+    <legend{{ legend.attributes }}>
       <span{{ legend_span.attributes.addClass(legend_span_classes) }}>{{ legend.title }}</span>
     </legend>
   {%- endif %}
diff -u b/core/modules/system/templates/form-element-label.html.twig b/core/modules/system/templates/form-element-label.html.twig
--- b/core/modules/system/templates/form-element-label.html.twig
+++ b/core/modules/system/templates/form-element-label.html.twig
@@ -5,7 +5,7 @@
  *
  * Available variables:
  * - title: The label's text.
- * - title_display: Element's title_display setting.
+ * - title_display: Elements title_display setting.
  * - required: An indicator for whether the associated form element is required.
  * - attributes: A list of HTML attributes for the label.
  *