For Chinese users, iCloud is operated by Cloud Big Data Industrial Development Co., Ltd.

My understanding is that Chinese users in mainland China have a different set of product terms that are vague or silent about certain privacy features or what the the Chinese partner does.

If you are a foreigner, you use the Apple owned service.

What I don’t know is where you connection terminates. With Microsoft, depending on the type of cloud, Office 365 TLS connections terminate at a local Microsoft point of presence. So you are in clear text outside of your jurisdiction for a limited period of time. (Not sure about China, but I’ve verified for other countries.)

Bottom line, if I had information of interest to Chinese interests, I wouldn’t expose an account with that data there or would get real paid advice about how to do it.