Index: src/wp-includes/query.php
===================================================================
--- src/wp-includes/query.php	(revision 37080)
+++ src/wp-includes/query.php	(working copy)
@@ -268,7 +268,7 @@
 }

 /**
- * Is the query for an existing taxonomy archive page?
+ * Is the query for an existing custom taxonomy archive page?
  *
  * If the $taxonomy parameter is specified, this function will additionally
  * check if the query is for that specific $taxonomy.
@@ -277,6 +277,8 @@
  * this function will additionally check if the query is for one of the terms
  * specified.
  *
+ * Is false for built-in taxonomies.
+ *
  * @since 2.5.0
  *
  * @global WP_Query $wp_query Global WP_Query instance.