Alerts are designed to notify users when specific conditions are met by a query's results. For custom notifications, especially those requiring detailed information like the count of duplicate records, a custom template is necessary. The QUERY_RESULT_ROWS variable is specifically designed to include details about the rows returned by the query, making it the correct choice for this scenario. Custom templates allow for the inclusion of dynamic data through built-in variables and support HTML formatting for better presentation of the alert details.