AS ignored in case SQL_CALC_FOUND_ROWS/FOUND_ROWS()

In case SQL_CALC_FOUND_ROWS are used, in the following SELECT FOUND_ROWS() AS totalnums, AS is ignored. It’s correctly set without HyperDB.

global $wpdb;

$sql = "SELECT SQL_CALC_FOUND_ROWS ID FROM wp_posts LIMIT 1";
$wpdb->get_results($sql);

$sql_total = "SELECT FOUND_ROWS() AS totalnums;";
$total_records = $wpdb->get_results($sql_total);

print_r($total_records);

array (size=1)
  0 => 
    object(stdClass)[4079]
      public 'FOUND_ROWS()' => string '3' (length=1)