Well, posting the actual content publicly would obviously make it public, which registering a hash on the blockchain would not. "Sending it to yourself through the mail" would probably be the competition, and I would say a cryptographic hash is at least as good as a postmark, as well as cheaper.

Anyway. I wasn't talking about NFTs as they exist today. I'm just saying the original concept (as I understood it) seemed basically reasonable, before everybody went insane.