This is a bit of an interesting question actually. Because in reality these IOU's aren't much different from a loan. And failure to pay a loan is punished pretty severely by china's Social credit system: https://en.wikipedia.org/wiki/Social_Credit_System . So in theory it perhaps shouldn't be too hard to punish people for this, but then again I don't really know too much about the chinese financial system.
Is this really a big issue? The current spread between CNY and CNH is less than a third of a percentage point.
Capital controls in general might be keeping CNY (and CNH) stronger than it would be otherwise.
[0] https://currenxie.com/blog/how-to-take-advantage-of-the-cny-...
[1] https://twitter.com/adamscrabble/status/1094717028009689089
Different rules apply.
1. Things are very different in China. If you can get away with not paying, it's not really wrong in the same way as in America. They have a different business culture based more around mutually assured destruction.
2. China has a massively leveraged internal economy, propped up by massive stimulus with the RMB. Only because of the two-currency BS they pull can they continue making this work. But because external nations don't actually use RMB, they could end up having a worse recession because of it. Or maybe better, because of the two currencies. Honestly, it's hard to know.
3. It's much harder to enforce these in China (unless you have the right connections, in which case you probably don't need to go through normal courts any way).
I'm not saying it's a bad idea, and I'm all for it in principle. I guess these are really more general issues with China and her economy which incidentally apply to this than issues with the concept.