IIRC, large customers--and China's Govt is one of them--have access to the Windows source code so safety and security probably aren't the top concern. They can surely audit the code, they have the expertise, money and manpower.
My guess is that US and China went to war over cyber-spying...
Nobody but Microsoft and perhaps the US government has access to all the Windows source code, and nobody outside of Microsoft has the ability to build a runnable Windows.
My guess is that US and China went to war over cyber-spying...