Thanks for those links.
Xiaomi works differently and I think they might probably get a 0 score from Computerworld since they rarely update the underlying Android OS to a new big version. Instead, they usually update their MIUI layer on top of that. However, they do roll in Android's security updates into their MIUI updates.
For example, my Xiaomi Redmi Note 3 phone got updated a few days ago. It is still on Android 5.1.1, but the Android security patch level is at 2016-07-01.