Recent Windows is remarkably hostile, see my comment there. As a Linux user for decades, I was horrified. Awesome move from China.
Also, it's also been happening in Europe for all public stuff slowly but surely; here in France, for example, all computers for the National Assembly run Linux (Ubuntu specifically); also, all cops' precincts are now using Linux as well (a publicly funded custom distribution, GendBuntu).
Given the US's hostile public stance towarda China it only makes sense that the Chinese gov't stops using an American OS. I would be surprised if the US didn't have a backdoor into Windows.