I did not know that an App can modify system behavior like this.
I have phone always on silent. I installed "Xiaomi Wear". During installation in Play Store, the phone made a short vibration. I thought that was weird, since the phone is on silent, and it never vibrates.
Anyway, after installation, the phone is now changed to vibrate every time I unlock it. A short vibration, but with full force (unlike when unlock with fingerprint).
Apparently, the phone scans NFC every time I unlock it - and since I have a bank card on the back, I guess it vibrates to signify it found something.
But I don't understand why an app can cause something like this, and how I can prevent it?