The games calculate horizontal FOV using as a reference the vertical FOV, which is fixed. The calculation is done not based on the resolution of the screen, but on the ratio between the height and the width (basically the aspect ratio). The higher the ratio is (the wider the image is) and the higher is the horizontal fov.
Which if you are obsessed by a minor increase in horizontal view, you can simple set your (1920x1200 monitor) resolution for that game to 1920x1080 and have the same thing. (equal)
And in all the other games that don't do this you will have more vertical screen area. (better)
And in every productivity application in the world you get more vertical screen area. (better)
