Blockchains are the systematization and democratization of that strategy. And those points are what technology is all about.
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Sure, to write our next shared article we can just have our Word files and call-up each other and exchange paragraphs over WhatsApp. Yet for some reason some people nerd out on unintuitive over-engineered CRDTs. That can't be useful to anyone, can it?
Perhaps in theory, but in practice it's not really true, especially with regard to the nature of information that is worthwhile to censor; the kind of situation where the powers-that-be would hack twitter to manipulate the timestamp of a hash string are very far-fetched.
You also introduce the risk of your message getting deleted, for whatever reason.
And these ways may also break your anonymity or leak your exploit if you're not careful.
A blockchain backed timestamp is simply better.
Suppose you post your finding generally, then I see it, and post it to the blockchain timestamped as my own. Then you say, “hey, I was first”. The blockchain is bad here because it’s incomplete.
If we mandate that only the blockchain can determine truth, then, if I really want to own that claim, I can hit you with a wrench until I have the private key, and now I am the owner of truth.
Trustless societies suck. We should be trying to increase social trust.
For that you need to publish your encrypted message that's somehow connected with a timestamp. If you can you might be able to get it included in a journal or a newspaper (which is what Robert Hook did in 1660), or use a trusted third party that verifies your timestamp.
Embedding a hash of your message in the blockchain is another way, which is arguably easier, more secure and trustless.