I remember reading
https://marginalrevolution.com/ back around the time of the 2008 financial crisis. Tyler Cowen was emphasizing the futility of trying to regulate the financial system. The banks paid big money to hire the smartest guys; the regulators had to make do with who they could get. The Collateralized Debt Obligation genie was out of the bottle and you couldn't get it back in.
One has to wonder how that looks from China. The government of the USA looks impressively powerful, yet it lost control of the financial sector. Some players in the American financial sector believed in CDOs and lost their own money. Others saw it as just another scam, with private profits and socialized losses.
To Chinese eyes that probably looks like corruption with extra steps. In particular, the US government could retain some legitimacy with a "Wall Street" versus "Main Street" narrative. Sure, Uncle Sam got ripped off by bankers, but what can you do?
The Chinese government is worried that corruption will cause it to lose its legitimacy with the Chinese people. But the Chinese people won't let the Chinese government away with the "It is the Banksters not the Officials." line. They don't see the top people as two warring clans, with Bankers beyond the reach of discipline by Officials.
So the Chinese government has to look several moves ahead. First come the CDOs. As the bubble builds the government finds that it is trapped: too many people are dependent on easy money for the government to pop the bubble. As the bubble inflates, the government tries to regulate its way out of trouble by deflating the CDO bubble. Here the Chinese government has second-mover advantage. It can see that the US government lost control and could not do anything, not even close. Eventually the bubble pops, leading to a financial crisis and the Chinese government gets the blame. It must have noticed that the US government didn't manage to shift the blame with long prison sentences for bankers, the US government had somehow lost control.
So I don't think that "absolutely allergic to unsecured debt." is quite it. My guess is that the Chinese government sees the US government losing control of the financial sector, years (ten? twenty?) ahead of the financial sector misbehaving and causing a government-shaking crisis. The Chinese government don't want finance building itself up as a separate (and irresponsible) power center. The American experience is that this happens slowly, little by little, but on a ratchet. A ratchet with a magic pawl that the government cannot lift. So the Chinese government has to nip it in the bud.