diff -u b/core/modules/migrate/src/Plugin/migrate/id_map/Sql.php b/core/modules/migrate/src/Plugin/migrate/id_map/Sql.php
--- b/core/modules/migrate/src/Plugin/migrate/id_map/Sql.php
+++ b/core/modules/migrate/src/Plugin/migrate/id_map/Sql.php
@@ -174,9 +174,6 @@
   /**
    * Retrieves the hash of the source identifier values.
    *
-   * It is public only for testing purposes. The source id values should be
-   * ordered in the same order as the data returned by a source plugin's
-   * getIds() method.
    * @internal
    *
    * @param array $source_id_values