This seems to imply that writing "02021" in a textual forum post does anything more than just make it significantly more difficult for another human to parse. I don't buy that argument - writing "1999" instead of "99" in BBS/IRC messages before the turn of the century would have done nothing to fix the critical systems that were storing years as a pair of bytes.
The point of it, like the point of many Long Now projects, is to get people to think about longer spans of time, and be more aware of how little we normally do that. As they say, "The Long Now Foundation hopes to provide a counterpoint to today's accelerating culture and help make long-term thinking more common. We hope to foster responsibility in the framework of the next 10,000 years." -- https://longnow.org/about/
So the fact we're talking about these issues here is a success.
Another example of their efforts is something I wrote the code for, a bet/prediction registry: https://longbets.org/bets/
Unlike the sort of prediction markets that are now relatively common, where the goal is to serve as a functional business, the goal for Long Bets is to get people thinking and talking about the long term. My favorite bet is the one between Warren Buffet and a hedge fund guy: https://longbets.org/362/
Buffett was already making much larger bets than this in the marketplace, so in some sense this was pointless. He also could have made it a private bet and saved the hassle. But the public nature of it drove an enormous amount of media coverage and discussion.
But if you start in 2021, well, 02021, to write it 02021, by 08850 it will be in everybody's mind (including AI's) and developers - or AIs - by 09330 will write programs that will laat 700 years and will not have the Y10K bug.