Batch won't execute in ldap_authorization_og_uninstall()

The function ldap_authorization_og_uninstall() is designed to remove the traces of the module from user accounts.

/**
 * Implements hook_uninstall().
 */
function ldap_authorization_og_uninstall() {
  module_load_include('inc', 'ldap_servers', 'ldap_servers.user_data_remove');
  batch_set(ldap_severs_user_data_setup_batch('og_group'));
  $batch =& batch_get();
}

function ldap_servers_empty_user_data($start, $step, $consumer_type, &$context) {
  [..]
          unset($account->data['ldap_authorizations'][$consumer_type]);

However, after running drush pmu ldap_authorization_og, the entries on user accounts are still there.
E.g. on user/123/devel I see $user->data['ldap_authorizations']['og_group'] === array().
Yes it is an empty array, but the code in ldap_servers_empty_user_data() suggests that the ['og_group'] key should be completely gone after the uninstall.
Also the uninstall happened suspiciously fast. Looping through all user accounts cannot be that fast!

Maybe the idea is that cron will execute the batch process?
I currently don't know enough how Drupal batch works to tell if this would be the case or not.

If it is NOT the case then this uninstall hook is broken.
If it IS the case, then this would mean that a user cannot safely remove the module after uninstall, because the batch might not be finished yet.