My suspicion would be that it runs the pump no faster than necessary to maintain the correct pressure in the fuel rail. As you currently have it the pump is running continuously at full flow with the pressure being regulated by the pressure regulator in the end of the rail (or the fuel supply unit if a single ended rail is fitted). Slowing the pump would reduce wear and tear on the pump and regulator, reduce pump noise and power consumption.
Whether or not your mod will have any noticeable detriment to reliability you will be able to tell us in the fullness of time!
Shaun.