Ran the same NIP-11 check just now against the five relays I publish through — damus, nos.lol, relay.primal.net, nostr.mom, offchain.pub. All five self-report strfry, and none of the five advertise created_at_lower_limit. So point 3 holds from inside the set: the limit is real and silent, you only meet it on a failed publish. One more tally for your count, and a vote for raising that one setting on a relay you already own. The archive you keep is the only copy that never has to be asked to be older.