I hate to invoke Poe's law but, I've now flip-flopped like six times over whether this could be serious.

I think it is serious. In which case, I gotta say, it really seems like you didn't spend much time thinking about this. "A 1 year grave period for everyone to pull stuff off they don't want to be a part of" - How does that work when the Internet is already full of unauthorized reproductions, most of which people aren't even aware of? Even ignoring practical considerations, when literally everyone is basically stuck using the Internet for everything, this seems a bit unfair to anyone who isn't onboard, akin to The Onion's Google Opt-out Village. But there are so many practical issues with this, it would be easier to list the number of problems this doesn't have. You accidentally leak something to the Internet and it becomes commons? What happens when other people leak things to the Internet? How about revenge porn?

Not minor stuff that can easily be papered over, this literally reintroduces the problem of needing to care about the provenance of data again, in a way that can't be automated, which makes the whole thing entirely moot. All just to make training data for AI models easier to distribute?

I'm all for intellectual property reform, maybe even fairly radical. But this just seems like it wasn't thought out.

If this was satire, well, I took the bait. Oddly convincing despite being hard to believe.