nvidia - Why does Ubuntu list my Intel Graphics drivers as Unknown:Unknown (not recommended)?

I've a laptop with Intel Graphics 520 (Skylake 6500U) and Nvidia 940MX.

I've installed the proprietary Nvidia driver (375.66) and it works fine. Also, I can switch between Intel and Nvidia graphics through the Nvidia Control Panel.

But why does Ubuntu list the Intel Graphics driver as Unknown:Unknown and why is it not recommended like the Nvidia driver?

Why is it saying "This device is using an alternative driver."? How can I install and configure the Intel Graphics driver such that it is both recommended and listed as Intel?

The OS is Ubuntu 17.04 (x64) and it is fully updated.