It's an extremely complicated peripheral, but it's still a peripheral. It's a monitor with an intricate tracking system that allows it to tell the PC powering it its exact location and orientation within a limited area. Playing a VR game is nothing like playing a game on a 3D monitor, it feels like you've been transported to another dimension, but the hardware itself isn't doing anything to execute the game and is still "just" a peripheral like a keyboard, monitor, or gamepad. It's just being fed what it should display by the PC and feeding the PC back information about its location and orientation. That's why Oculus initially needed to put a hardware check into their DRM to block shims like this, there's no real technical reason you can't use one in place of the other once you translate its I/O.

it's a display, there are outputs of location data to the computer but they don't come from the headset, they come from other peripherals.

if I then plug the display into my video card; then that makes it a head mounted monitor with drivers to output data specific to that display.

Vr games work fine with traditional displays, I've seen plenty of screenshots on my traditional display. It isn't pleasant or immersive that WA, of course.