diff -u b/core/lib/Drupal/Core/Config/Schema/Sequence.php b/core/lib/Drupal/Core/Config/Schema/Sequence.php
--- b/core/lib/Drupal/Core/Config/Schema/Sequence.php
+++ b/core/lib/Drupal/Core/Config/Schema/Sequence.php
@@ -33,9 +33,10 @@
    * Gets the description of how the sequence should be sorted.
    *
    * @return string|null
-   *   Describes how the sequence should be sorted. Either 'value', 'key' or
-   *   NULL. NULL means that the schema does not describe how the sequence
-   *   should be sorted.
+   *   May be 'key' (to sort by key), 'value' (to sort by value, discarding
+   *   keys), or NULL (if the schema does not describe how the sequence should
+   *   be sorted). Only the top level of the array is sorted. Top-level keys are
+   *   discarded when using 'value' sorting.
    */
   public function getOrderBy() {
     $definition = $this->getDataDefinition();
diff -u b/core/lib/Drupal/Core/Config/Schema/SequenceDataDefinition.php b/core/lib/Drupal/Core/Config/Schema/SequenceDataDefinition.php
--- b/core/lib/Drupal/Core/Config/Schema/SequenceDataDefinition.php
+++ b/core/lib/Drupal/Core/Config/Schema/SequenceDataDefinition.php
@@ -13,9 +13,10 @@
    * Gets the description of how the sequence should be sorted.
    *
    * @return string|null
-   *   Describes how the sequence should be sorted. Either 'value', 'key' or
-   *   NULL. NULL means that the schema does not describe how the sequence
-   *   should be sorted.
+   *   May be 'key' (to sort by key), 'value' (to sort by value, discarding
+   *   keys), or NULL (if the schema does not describe how the sequence should
+   *   be sorted). Only the top level of the array is sorted. Top-level keys are
+   *   discarded when using 'value' sorting.
    */
   public function getOrderBy() {
     return isset($this->definition['orderby']) ? $this->definition['orderby'] : NULL;
diff -u b/core/lib/Drupal/Core/Config/StorableConfigBase.php b/core/lib/Drupal/Core/Config/StorableConfigBase.php
--- b/core/lib/Drupal/Core/Config/StorableConfigBase.php
+++ b/core/lib/Drupal/Core/Config/StorableConfigBase.php
@@ -218,9 +218,11 @@
           case 'key':
             ksort($value);
             break;
+
           case 'value':
             sort($value);
             break;
+            
         }
       }
     }
diff -u b/core/tests/Drupal/KernelTests/Core/Config/ConfigSchemaTest.php b/core/tests/Drupal/KernelTests/Core/Config/ConfigSchemaTest.php
--- b/core/tests/Drupal/KernelTests/Core/Config/ConfigSchemaTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Config/ConfigSchemaTest.php
@@ -396,7 +396,7 @@
   }
 
   /**
-   * Test configuration sequence sorting using schemas.
+   * Tests configuration sequence sorting using schemas.
    */
   public function testConfigSaveWithSequenceSorting() {
     $data = [