In changeset 08f8301b216, Barney Gale wrote os.listdir as a replacement for the “accessor” tooling. According to Antoine Pitrou, its original purpose was to create race-free access to the directory.
Are you sure that code won’t be broken by removing the materialization feature? Will the loss of atomicity not matter to anyone? How about the deferred resource finalization? Perhaps @pitrou can opine before you made this possibly breaking change.