Microsoft wont say what or why they have to modify Windows 10 for China, but I'd imagine you could easily appease government officials just by redirecting all the user data Windows 10 collects to the Chinese government instead of Microsoft. 😀
Microsoft Corp. has finished development of a Windows 10 version customized for Chinese government use, which could boost its China prospects after sales were hit by Beijing’s cybersecurity crackdown. Microsoft declined to say how the software was modified, but in general China’s government is concerned about technology products that could contain hidden “backdoors” to enable foreign surveillance.