During the purge, delete URL with status = 31 ?

Currently, during a purge, we delete old URLs if the status code is not a two-digit number (meaning there was a problem) or if it is a two-digit number starting with 5 (permanent failure).

May be we should also delete when status code = 31, meaning a permanent redirect. To quote the spec "Tools like search engine indexers or content aggregators should update their configurations to avoid requesting the old URL,"