This does a lot less than what most people think it does...
I must prove that I was the first person to come up with an idea.
so long as I can show that I published the content first
And yet what the poster goes on to describe does not actually accomplish that. (and, technically, as an aside being first it not really as relevant for copyright, since independent creation is possible and permitted)
Say you invent something. Now I can go timestamp it. And claim to have invented it.
Say you invent something and timestamp it. I can say "I invented it first, he just timestamped a copy of my idea."
We can both timestamp the same thing (or substantially the same thing) and interdependently go show our timestamps to third parties who will never be aware of the other claim.
These ideas are not new... people were commuting to things back in 2010. These ideas reoccur ever couple of months when people don't bother to do any research and see it's all been done before... people just lose interest in it because its limited enough that the value isn't so great.
Worse, most of the reoccurring proposals are highly inefficient (e.g. require a transaction per commitment, when technically no transactions are required _at all_ to get timestamps), or even outright insecure. (Competent folks have mostly given up reviewing ideas from people who don't spend even a moment doing research.)