Xiaomi smartphones do in fact upload user data without their permission/knowledge
Considering that half the apps out there (and I mean benign/legitimate apps!) seem to upload user data without user's knowledge, that is not so shocking. Once you start using your phone, several apps will start siphoning your data.
Recent "simplification" of Android Google-store permissions means that I don't even know how much of a permission I am giving to a new app.