Restrict bundles for "Add new" (taxonomy term, etc) when "Add existing" is powered by an entity reference view

i think this is code i was starting to add related to this, throwing it here for now will delete if it doesn't make sense.

/**
 * Gets the bundles for which the current user has create access.
 *
 * @return string[]
 *   The list of bundles.
 */
protected function getCreateBundles() {
  $create_bundles = [];
  foreach ($this->getTargetBundles() as $bundle) {
    if ($this->getAccessHandler()->createAccess($bundle)) {
      $create_bundles[] = $bundle;
    }
  }
  $allowed_bundles = ['sources'];
  if ($allowed_bundles) {
    $create_bundles = array_intersect($allowed_bundles, $create_bundles);
  }

  return $create_bundles;
}

This is implemented in IEF Complex Open widget → for the time being, and here is how, this same change could work for IEF itself:

https://git.drupalcode.org/project/ief_complex_open/-/commit/6863903b015...