diff -u b/src/Context/FieldResolver.php b/src/Context/FieldResolver.php
--- b/src/Context/FieldResolver.php
+++ b/src/Context/FieldResolver.php
@@ -315,10 +315,12 @@
    * @return bool
    *   TRUE if any one of the given resource types is traversable.
    *
-   * @todo This class really shouldn't need to be aware of entity types and
-   * their definitions. Whether a resource can have relationships to other
-   * resources is information we ought to be able to discover on the
-   * ResourceType.
+   * @todo This class shouldn't be aware of entity types and their definitions.
+   * Whether a resource can have relationships to other resources is information
+   * we ought to be able to discover on the ResourceType. However, we cannot
+   * reliably determine this information with existing APIs. Entities may be
+   * backed by various storages that are unable to perform queries across
+   * references and certain storages may not be able to store references at all.
    */
   protected function resourceTypesAreTraversable(array $resource_types) {
     foreach ($resource_types as $resource_type) {