Edit: The viewing angle is 57 degrees. In comparison most VR headset have a viewing angle of 90-110 degrees.

FOV shouldn't be ignored, but having a large FOV also isn't necessarily desirable on a HMD. It's important for VR, because a major point of that is filling one's peripheral vision, creating a sense of immersion.

But if you wanted, say, an HMD as a monitor replacement

something that I'd be interested in

it doesn't buy all that much, because the stuff that you can see with high detail is only in a small cone in front of you. For a given pixel resolution, I'd rather have a smaller FOV on an HMD for that, because you can take advantage of fairly high angular resolutions within that narrow cone. The real bottleneck on an HMD as a monitor replacement is the limited angular resolution you get

you can't have something that gets as sharp and crisp as existing conventional monitors.