The best litmus test is "is telling which document was earlier helping in anything?", because this is precisely what blockchain is solving.

The use-case here is a decentralized mechanism for providing (at least approximately) validated timestamps, which it seems to me a blockchain can do.

... Why? Why would a bad choice of algorithms and specious "security" guarantees be a better choice tomorrow?

> And who will be well-positioned then?

Whoever discovers a worthy use for a blockchain.

Point taken, but in the meantime there’s a lot of effort being wasted in awkward pairings.