It is obviously saliently true just via direct experience. Your eyes focus at different distances when looking at 3d objects in VR. You can feel it!

I am not a physicist by any means, and I am not sure what a "light field" exactly is in terms of engineering, but as a everyday skeptic I am generally rather wary of anything Magic Leap puts out.

You are confusing optical focus (like a camera lens or the lens in your eye) with stereopsis - the mechanism by which your brain detects depth information through parallax.

The VR headset shows each eye a slightly different image. Objects appear in slightly different locations in each image. When you look at these virtual objects, the relative angle between your eyes changes which creates the illusion of depth. (This is my layman understanding. I am open to correction).

The optical focal distance remains constant, however.

I've followed up and verified that indeed, most all VR displays have a static focal distance. Thank you for taking the time to correct my and others misconception on the topic!

Nah, they have fixed focus (I think at infinity, but that might not be true). You use other depth cues in normal VR systems, but not focal depth.