diff -u b/core/lib/Drupal/Core/Config/Entity/ConfigEntityInterface.php b/core/lib/Drupal/Core/Config/Entity/ConfigEntityInterface.php
--- b/core/lib/Drupal/Core/Config/Entity/ConfigEntityInterface.php
+++ b/core/lib/Drupal/Core/Config/Entity/ConfigEntityInterface.php
@@ -82,19 +82,24 @@
   public function status();
 
   /**
-   * Returns if this entity is being changed as part of an import process.
+   * Returns whether this entity is being changed as part of an import process.
    *
-   * Code that makes persistent changes to new, changed, or deleted
-   * configuration entities, but not imported entities that may already contain
+   * Code that makes changes to configuration or the entities that are being
+   * changed, but not imported entities that may already contain
    * these changes, must check this method.
    *
-   * An example is \Drupal\node\Entity\NodeType::postSave(), which adds the
-   * default body field to newly created node types. Imported entities already
-   * contain this field from when they were originally created, and must not
-   * get it again.
+   * An example of code that must not be executed is
+   * \Drupal\node\Entity\NodeType::postSave(), which adds the default body field
+   * to newly created node types. Imported entities already contain this field
+   * from when they were originally created, and must not get it again.
+   *
+   * An example of code that must be executed both for imported and non-imported
+   * entity changes is \Drupal\field\Entity\FieldInstance::postSave(), that
+   * makes sure the caches are emptied whenever any field instance change is
+   * made.
    *
    * @return bool
-   *   TRUE if the configuration entity is being created, updated or deleted
+   *   TRUE if the configuration entity is being created, updated, or deleted
    *   through the import process.
    */
   public function isSyncing();