What hardware are people using to run modern VR?
1440p (2560x1440) is 3,686,400 pixels.
2160p (2160x2160) is 4,665,600 pixels, per eye, so 9,331,200 pixels.
This headset will require a million more pixels to be rendered than 4K. 9 Million pixels @ 144hz is no easy task.
My RTX 4080 (9800X3D) struggles with 4K gaming.
You render lower quality and scale the images up to native resolution, with filters to reduce any jagged artifacts. It's not ideal, and so even running at the "same" resolution, the 2d monitor looks better then it does in the headset.
But the immersion is enough that you forget about it and just enjoy the content, as long as it's comfortable enough