diff -u b/core/lib/Drupal/Core/Entity/TypedData/EntityDataDefinition.php b/core/lib/Drupal/Core/Entity/TypedData/EntityDataDefinition.php
--- b/core/lib/Drupal/Core/Entity/TypedData/EntityDataDefinition.php
+++ b/core/lib/Drupal/Core/Entity/TypedData/EntityDataDefinition.php
@@ -28,14 +28,14 @@
         $data_type .= ":{$bundle}";
       }
 
-      // If the definition doesn't exist, just create from defaults.
+      // Load definitions created by the EntityDeriver.
       $values = \Drupal::typedDataManager()->getDefinition($data_type, FALSE);
       $definition = new static(is_array($values) ? $values : []);
 
-      // Set the passed entity type.
+      // Set the EntityType constraint using the given entity type ID.
       $definition->setEntityTypeId($entity_type_id);
 
-      // Set the passed bundle, if it was given.
+      // If available, set the Bundle constraint.
       if ($bundle) {
         $definition->setBundles([$bundle]);
       }