This thing that the frequencies with the same voltage have the same power consumption is wrong.
The formula for power consumption of an actual processor is very complicated, but for the sake of simplicity it's better to assume that the power consumption has a linear growth in relation to the frequency (f) and a quadratic growth in relation to the voltage (v^2).
With the CPU awake (not in deep sleep), it's always better to be at a lower frequency. So it's not a good idea to have 480MHz as minimum clock if you do tasks that keep your phone awake all the time (I think listening to music with the screen off keeps the phone awake, so it's a good example).
But in an usage where the only things the phone does with the screen off is like syncing your data, it's possible to set a higher minimum clock (like 480MHz) and make the phone stay awake for a shorter time for these syncing activities (meaning a longer time in deep sleep), thus giving an increase in battery life.
Just press the 'Thanks' button in case I was helpful