Information in "bt_torrents" table for local torrents is not updated, why?

As I can see, information in "bt_torrents" table for local torrents is not updated.
When cron runs

function bt_torrent_cron() {
...
  if (module_exists('bt_tracker')) {
  ...
    $scrape_info = module_invoke('bt_tracker', 'scrape', $torrent->info_hash);

bt_tracker_scrape then invokes:

function bt_tracker_scrape($info_hash) {
  if (variable_get('bt_tracker_scrape_scope', 0) == 0) {
  ...
    $response = db_fetch_array(db_query("SELECT ... FROM {bt_torrents} ..."));

Then bt_torrent_cron() UPDATE data for bt_torrents table from itself.

db_query("UPDATE {bt_torrents} SET ...", $scrape_info['complete'], ...);

Then I see

else {
  $response['complete'] = db_result(db_query("SELECT COUNT(btau.ip) FROM {bt_tracker_active_users} btau WHERE ..."));
  ...

and this part do what need`s to be done, but never invokes because of undefined "bt_tracker_scrape_scope" variable.

What this variable mean? It is a depricated or not yet implemented variable?