Sorry, I wrote it in a bit of a hurry and it ended up not too terribly clear. It isn't exactly that bonds aren't safe, it's more that there are two kinds of bonds: bonds that will expire soon (1-4 years) and bonds which will take longer to expire (think 10, 20, 30 years). Bonds have a price when they're issued by the government (or by a private company): say, $1000. People buy those bonds, which then have to be repaid at the expiration date, when the bond "matures". This, essentially, is a loan: government (or a private company) gives you a piece of paper promising to pay you back, and you give government money.
Bonds, as most loans, have interest rates. These rates are fixed as to the value of the bond when it was issued. Say our bond had a 10% interest rate; this means every year the government would have to pay you back (in installments, over the course of the year) $100. This is nice. You don't have to do anything and you'll get money. Obviously interest rates are typically shit, which means bonds are a shit investment, because gambling on Tesla will probably give you better immediate returns (or, more realistically, an index fund, which is nothing but a collection of different investments bundled together).
Bonds, once issued, become property; they can be resold to someone else. Their "yield" is based on this. Say a bond is close to expiring: this means it'll pay back its value soon. This makes it a more desirable bond, since it probably will be repaid and this you'll get your money back. This typically make short-term bonds worth more, say $1100, on the market. Thing is, the bond still pays only $100 every year. This means its yield has (relatively) gotten lower: to 9.09% (since you paid more). The higher the bond price, the lower the yield; it's a simple relation. As such, long term bonds are usually cheaper, since there is a bigger chance something will happen before the bond matures which could make it fail (i.e. not pay its value back). They are, as such, "riskier".
Thing is, some porkies aren't dumb; they can see the writing on the wall (maybe they read a bit of marx when they were young…) This means they know the stock market is looking a bit shaky; maybe parking a bunch of cash on Tesla right now is a bad idea. They look for a safer place to put their money, even if it means smaller returns, just to insulate themselves from the crisis. Short-term bonds are nice, but maybe the crisis will last longer than the bond has before expiring, which would leave you with a bunch of cash which is gonna need to look for an investment, which may be more difficult or more expensive. Long-term bonds guarantee you'll have a nice, solid thing for a while, which you can then resell if you feel like things are better, or just wait for it to mature and get your money back.
You can now see the usual framework: on a direct relation, short-term bonds are usually more expensive than long-term bonds; their yield is lower, therefore, that that of the long-term bonds. But before every single recession, apparently, something happens: the yield on short-term bonds goes higher than that of the long-term bonds, or, as they call it, "the curve inverts" (which is based on the yield curve graph, as can be seen annexed to this post). This is, essentially, porky's own measure of confidence on the near-future of the market: they think it'll go bad soon, so they're parking their money so that papa government will guarantee it no matter what. For marxists this is essentially a good enough indicator that it isn't just crazy communists that think shit's gonna hit the fan soon: porky also thinks that as well. And if porky thinks shit's gonna hit the fan, they you better bet it will.
As a side note, the Fed keeps doing Quantitative Easing (QE), which essentially amounts to buying (technically swapping) a bunch of assets (usually shit assets in the balance sheets of banks and companies) with money they can technically print by doing this. This has caused enormous hyperinflation in the stock market (and also bitcoin, most notably), since porky just takes this money, makes some stock buybacks and gives itself in dividends, which is a tidy little business. Problem is the Fed is getting enormously swamped with shit assets (i.e. debt), and the stock market has gotten so crazy that any crash is gonna be so volatile as to devastate the economy (since a great deal of companies that should have died in 2008 are still alive as "zombies"). Until the Fed stops doing this, a crash is unlikely; the question is when will their hand be forced (since they cannot decide to crash the market, for obvious reasons).
As for China dumping bonds, they probably are, but as Peruvian Bull noted on the posts shared by GME Anon, they have massive dollar surpluses since the US buys their shit (and all other shit) in dollars. They have to do something with those dollars, otherwise their currency will devalue (from having too many dollar holdings, because the dollar is the de facto reserve currency of the world) which would fuck their export economy up. So they usually just give them back to the US and get shitty bonds in return, which is better than holding dollars. It seems like they're buying gold from Russia https://thedeepdive.ca/the-de-dollarization-frenzy-china-covertly-buying-gold-to-reduce-us-dollar-exposure/
, but it's hard to say how relevant it is right now. It's tough to de-dollarize. (Yves Smith has a great article about this: https://www.nakedcapitalism.com/2022/12/dethroning-the-dollar-why-the-alternatives-are-not-ready-for-prime-time.html
). The moment will come, but it's probably not too soon just quite yet, unless some crisis (cough cough Taiwan) forces their hand, like the Ukraine crisis forced Russia's hand).