They don't do 4k mirroring. A 4k monitor has 8 million pixels while the googles have about 11 million pixels per eye. True 4k is only possible if you use 85% of vertical and 85% of horizontal FoV, like when staring at a 24" monitor from 15cm.

Even if they were double the resolution per eye, you aren't going to have "native" 4k reproduction because you are looking at a projection of a screen rather than an actual screen. What is the value of achieving one "accurate" pixel if it is surrounded by eight bilinear-interpolated ones?

But then, you usually don't buy a 4k screen because you can perceive the individual pixels either, unless you are creating content that requires that.

I suspect it aligns easier with the quality concerns of reality and not with virtual components - if I can use a monitor through the screen with no noticeable loss of quality or additional eye strain, there's no reason to think a virtualized monitor won't be at least as good.

I don't think it's an apples to apples comparison (heh), I think at this point 'good enough' is going to be better than anything my eyes can resolve. On a Quest 3 with Zenni lenses, pixel visibilty as a concern is way down on my list. It works REALLY well.

8/11 = 73% not 85%. so should be a lot more comfortable distance than 15cm/5.9 inches.

Nope.

0.85*0.85 => 0.73

Ah, gotcha. But what if you factor in the limited FOV of the display itself? this 11 million pixel calculation doesn't apply to the full FOV of the eye after all.

I would expect most people to pick a natural size for their windows, perhaps 24-30" half a meter away?

It's a VR headset, angular resolution is fixed at 3800 px / 90 deg = 42px/deg. For a 27.5" virtual display half a meter away, let chord length = 700mm, radius ~ 600mm, distance to virtual display will be 488mm, and diagonal angle it occupies within view will be 71.4deg. with 42px/deg, resolution is ~3000px diagonal, or from (16x)^2+(9x)^2 = (3000)^2, x = 163.4, therefore resolution for that virtual monitor will be 2608x1470.

Other combinations of distances and virtual sizes can be calculated in the same manner.

How much of that “natural size” has been dictated by common monitor sizes, the limits of desk size/setup, and aesthetics?

My work setup as a 43” monitor set about 1 arm’s length away. I can just touch it when my fingertip if I stretch slightly. In a virtual space, I’d probably go slightly larger, maybe 45-48”, pushed a little further back.

I don't think I would want a monitor that big, since I think I would have trouble covering all of it without moving my head.

So then it's not "4k mirroring".