ambiguous parameter in hook_field_attach_delete_bundle()

API page: http://api.drupal.org/api/drupal/modules%21field%21field.api.php/functio...

Enter a descriptive title (above) relating to hook_field_attach_delete_bundle, then describe the problem you have found:

> $bundle: The bundle that was just deleted.

Is that a bundle machine name or an array? It's ambiguous.

Looking at the invoker, it seems to be a string:

// Clear bundle display settings.
  variable_del('field_bundle_settings_' . $entity_type . '__' . $bundle);

  // Let other modules act on deleting the bundle.
  module_invoke_all('field_attach_delete_bundle', $entity_type, $bundle, $instances);

TBH the parameter could possibly do to be renamed $bundle_name, as that's used elsewhere in core when a bundle string is meant.