Which is why that data should not be collected.

While I disagree with OP, that kind of information isn't classified. It's personally identifiable information which is restricted and secured, but it's not classified in the same sense as the person who leaked on discord.

In response to op, there are plenty of legitimate reasons to classify information that are not nefarious. For example, a diagram explaining the security systems for a building. It's better to restrict access to that document so it is less likely for an adversary to see the details, because all that would really do is enable them to identify weaknesses which they could exploit. Generally this sort of thing is called operational security and I think it is actually the basis for the US government's mandatory access control in the first place (e.g. "loose lips sink ships").

And? For the average country, the difficult thing about nuclear weapons is not how to build one (pipe with two halves and a bit explosives is enough for a few kt) but to get enough Plutonium. You know, the whole thing with Israel running secret facilities with ceramic centrifuges for years. What US and China are wasting a few MW computer center each year on, is getting a bit more out of it than the competition, especially fusion weapons. Seen rationally, it's a childish "i have the bigger ~~dick~~ boom".

And if all records had to be public, there would have been a hell of a lot lower chance of nuclear weapons being invented. Because who would want to give that weapon to everybody else as well as themselves?

I am a private citizen who has not been given power over the lives of other people. Therefore, I don't have to.