Add class Mage_Adminhtml_Model_System_Config_Backend_Seo

to change category flas and product flat indexers status to require_reindex when configuration changed

app/code/core/Mage/Adminhtml/Model/System/Config/Backend/Seo.php

@@ -0,0 +1,46 @@
+<?php
+/**
+ * Magento
+ *
+ * NOTICE OF LICENSE
+ *
+ * This source file is subject to the Open Software License (OSL 3.0)
+ * that is bundled with this package in the file LICENSE.txt.
+ * It is also available through the world-wide-web at this URL:
+ * http://opensource.org/licenses/osl-3.0.php
+ * If you did not receive a copy of the license and are unable to
+ * obtain it through the world-wide-web, please send an email
+ * to [email protected] so we can send you a copy immediately.
+ *
+ * DISCLAIMER
+ *
+ * Do not edit or add to this file if you wish to upgrade Magento to newer
+ * versions in the future. If you wish to customize Magento for your
+ * needs please refer to http://www.magento.com for more information.
+ *
+ * @category    Mage
+ * @package     Mage_Adminhtml
+ * @copyright  Copyright (c) 2006-2020 Magento, Inc. (http://www.magento.com)
+ * @license    http://opensource.org/licenses/osl-3.0.php  Open Software License (OSL 3.0)
+ */
+
+
+class Mage_Adminhtml_Model_System_Config_Backend_Seo extends Mage_Core_Model_Config_Data
+{
+    /**
+     * Refresh categories and products url rewrites if configuration was changed
+     */
+    protected function _afterSave()
+    {
+        if ($this->isValueChanged()) {
+            Mage::getModel('index/indexer')
+                ->getProcessByCode(Mage_Catalog_Helper_Category_Flat::CATALOG_CATEGORY_FLAT_PROCESS_CODE)
+                ->changeStatus(Mage_Index_Model_Process::STATUS_REQUIRE_REINDEX);
+
+            Mage::getModel('index/indexer')
+                ->getProcessByCode(Mage_Catalog_Helper_Product_Flat::CATALOG_FLAT_PROCESS_CODE)
+                ->changeStatus(Mage_Index_Model_Process::STATUS_REQUIRE_REINDEX);
+        }
+        return $this;
+    }
+}

app/code/core/Mage/Adminhtml/Model/System/Config/Backend/Seo/Product.php

@@ -21,12 +21,18 @@
 class Mage_Adminhtml_Model_System_Config_Backend_Seo_Product extends Mage_Core_Model_Config_Data
 {
     /**
-     * Refresh category url rewrites if configuration was changed
+     * Refresh products url rewrites if configuration was changed
      *
      * @return $this
      */
     protected function _afterSave()
     {
+        if ($this->isValueChanged()) {
+            Mage::getModel('index/indexer')
+                ->getProcessByCode(Mage_Catalog_Helper_Product_Flat::CATALOG_FLAT_PROCESS_CODE)
+                ->changeStatus(Mage_Index_Model_Process::STATUS_REQUIRE_REINDEX);
+        }
+
         return $this;
     }
 }

app/code/core/Mage/Catalog/etc/system.xml

@@ -262,7 +262,6 @@
                         </product_url_suffix>
                         <product_use_categories translate="label">
                             <label>Use Categories Path for Product URLs</label>
-                            <comment>Changing this option requires full reindex of "catalog_url"</comment>
                             <frontend_type>select</frontend_type>
                             <source_model>adminhtml/system_config_source_yesno</source_model>
                             <backend_model>adminhtml/system_config_backend_seo_product</backend_model>
@@ -273,9 +272,9 @@
                         </product_use_categories>
                         <create_url_for_disabled translate="label">
                             <label>Generate URL rewrites for disabled categories and products</label>
-                            <comment>Changing this option requires full reindex of "catalog_url"</comment>
                             <frontend_type>select</frontend_type>
                             <source_model>adminhtml/system_config_source_yesno</source_model>
+                            <backend_model>adminhtml/system_config_backend_seo</backend_model>
                             <sort_order>4</sort_order>
                             <show_in_default>1</show_in_default>
                             <show_in_website>0</show_in_website>