diff -u b/core/modules/update/src/ProjectCoreCompatibility.php b/core/modules/update/src/ProjectCoreCompatibility.php
--- b/core/modules/update/src/ProjectCoreCompatibility.php
+++ b/core/modules/update/src/ProjectCoreCompatibility.php
@@ -162,40 +162,19 @@
    * @see static::createMessageFromCoreCompatibility()
    */
   protected function createCoreCompatibilityDetails($core_compatible, $core_compatibility_range) {
-    $element = [
+    return [
       '#type' => 'details',
-      'compatibility_range' => [
+      '#title' => $core_compatible ? $this->t('Compatible') : $this->t('Not compatible'),
+      '#open' => !$core_compatible,
+      'message' => [
         '#markup' => $core_compatibility_range,
       ],
-    ];
-    if ($core_compatible) {
-      $element += [
-        '#title' => $this->t('Compatible'),
-        '#open' => FALSE,
-      ];
-      $compatibility_intro = $this->t('Your version of Drupal core (%version) is compatible with this update.', ['%version' => $this->existingCoreVersion]);
-    }
-    else {
-      $element += [
-        '#title' => $this->t('Not compatible'),
-        '#open' => TRUE,
-      ];
-      $compatibility_intro = $this->t('Your version of Drupal core (%version) is not compatible with this update.', ['%version' => $this->existingCoreVersion]);
-    }
-    $element += [
-      'intro' => [
-        '#weight' => -10,
-        '#markup' => $compatibility_intro,
-        '#prefix' => '<p>',
-        '#suffix' => '</p>',
-      ],
       '#attributes' => [
         'class' => [
           $core_compatible ? 'compatible' : 'not-compatible',
         ],
       ],
     ];
-    return $element;
   }
 
   /**