Help needed with rotation vector sensor

[oldschool63]

This is the usual description about the rotation vector sensor:

The rotation vector is a virtual sensor in Android that depends on the accelerometer, gyroscope and magnetometer (digital compass), using these inputs it is able to determine the orientation of the device.

I have 4 devices here, all 4 (according to the GPS Status app) have an accelerometer and magnetometer but no gyroscope. Yet 2 of the devices do have a rotation vector sensor and the other 2 devices do not:

Motorola Moto G (osprey): CyanogenMod 12.1 - NO rotation vector sensor
Samsung Galaxy Note 8.0 (n5110): Resurrection Remix 5.7.4 (cm13) - NO rotation vector sensor
LG G-Pad 7.0 (v400): Resurrection Remix 5.7.4 (cm13) - rotation vector sensor WORKING
Motorola Atrix HD (mb886): CyanogenMod 12.1 - rotation vector sensor WORKING

Obviously the presence of the rotation vector sensor is not a question of the CyanogenMod version (see above). On the other hand it is supposed to be a virtual (aka software) sensor.
So where exactly is that sensor implemented? And why is present on some devices and not on other devices? Any help pointing me in the right direction will be greatly appreciated.