I’ve not seen anything to indicate that the HoloLens is doing actual eye tracking. They have a Gaze metaphor that is the same “nose-mounted laser-pointer” style as Google Cardboard and Samsung Gear VR. But this article seems to be speculating that eye tracking could theoretically be done through the same prism that is being used to project the image into the eye, not that it actually is occurring.
And judging from the rather glaring grammatical errors in the rest of the article, I am inclined to believe the person is just a sloppy writer. I’ve had to deal with a lot of journalists and they typically don’t know anything about what they are talking about. That’s not a knock on journalists, that’s kind of the whole point of the job. Good journalists know how to write and get to the core of a story and relay details even if they don’t know anything about them going in to the story. I’m not convinced this person is a good journalist.
I have one on my head right now. I’m looking at the documentation right now. I don’t see any discussion of eye tracking.