> You earn risk-free 0.9% if you hold them in CNY. You lose 7% if you hold them in USD.
This is false, you are exposed to risk in changes in foreign exchange rates.
The yuan is pegged to the dollar, so it has the same exposure to fluctuations in fx that the dollar has. (Not to mention the fact that the Chinese government periodically adjusts its exchange rates)
This is false. Anyone's prediction for long term exchange rate is CNY's relative value to USD is getting higher, do note the PPP rate of CNY is around 3 for one compare to exchange rate roughly 6 for one. So unless you are doing super short term, these are fluctuations, not risk.
If you set USD as the base currency then there is going to be exchange, as such there will be fluctuations, so yes. Yet there is risk just holding on to USD as well, perhaps it wasn't so evident because you consider USD as the default.
Meanwhile in China, inflation is less than 1.5%, interest for money market fund is 2.4%.
You earn risk-free 0.9% if you hold them in CNY. You lose 7% if you hold them in USD.
Your choice now?