Omniture_set_variables does not seem to work

I am trying to use omniture_set_variabes, but looking at the code it does not look like this will set a variable unless that variable is also set using hook_omniture_variables

    $extra_variables = omniture_get_variables();

    if ($omniture_hooked_vars = module_invoke_all('omniture_variables', $main)) {
      if (isset($omniture_hooked_vars['header'])) {
        $header = $omniture_hooked_vars['header'];
      }
      if (isset($omniture_hooked_vars['variables'])) {
        // We need to merge some variables here.
        foreach ($omniture_hooked_vars['variables'] as $k => $v) {
          if (is_array($v)) {
            $v = $v[count($v)-1];
          }
          if (isset($extra_variables[$k])) {
            $v = $extra_variables[$k];
          }
          $extra_variables_formatted .= "$k=\"$v\";\n";
        }
      }
      if (isset($omniture_hooked_vars['footer'])) {
        $footer = $omniture_hooked_vars['footer'];
      }
    }

it seems that $v = $extra_variables[$k]; is the only place a value was pulled from $extra_variables
maybe a

    foreach ($extra_variables as $k=>$v) {
      $extra_variables_formatted .= "$k=\"$v\";\n";
    }

is needed?