Although rfc is not valid ISO code for any language at this moment, we should generally avoid three-letter interwiki prefixes for the sake of preventing posssible conflicts, as various codes are being added and changed during the time. (IIRC such conflicts already happened in past.)
Topic on Talk:Requests for comment/Future of magic links
RFC existed as an interwiki prior to this RfC.
I didn't say the opposite. I was pointing out that it should be considered to not use interwiki as a final solution due to possible conflicts.