[boltzmann-brain]

peripheries bulge out because of a flattened perspective. Think about what you'd see on a perfectly flat screen that takes up the same /horizontal angle/ across your vision. Note that by necessity, it would be physically longer than a curved display that takes up the same horizontal angle.

One degree if vision is pretty narrow in the center of that, but much wider on the far sides.

Those games are not correcting the projection for curved monitors at all. The widening on the sides is just an artifact of projecting onto a flat plane, which then gets wrapped around the curved monitor in a simple manner.