@Staglaitor
My best guess is the relative magnitude of the values you’re inserting - f-stop is a divided value, so any changes like this in the decimal place are going to be multiplying the aperture rather than dividing it. For the reason it changes sharpness - it really depends on the object in view at which distance.
The example f-stop values are from 1.4 - 6.0.
Camera and Cinematics require a lot of mathematics, not only on the side of the computer but the programmer, who needs to frame things that the camera will be able to record.
I hope some of this can help you out,
-Zen