Index: src/wp-includes/query.php
===================================================================
--- src/wp-includes/query.php	(revision 37079)
+++ 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.
  *
+ * Returns false for built-in taxonomies (category and tag archives).
+ *
  * @since 2.5.0
  *
  * @global WP_Query $wp_query Global WP_Query instance.
@@ -4326,7 +4328,7 @@
 	}
 
 	/**
-	 * 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.
@@ -4335,6 +4337,8 @@
 	 * this function will additionally check if the query is for one of the terms
 	 * specified.
 	 *
+	 * Returns false for built-in taxonomies (category and tag archives).
+	 *
 	 * @since 3.1.0
 	 *
 	 * @global array $wp_taxonomies