The MX60 regulates the output to the battery by changing the PV input voltage to somewhere between max power point and PV open circuit voltage, or completely off (disconnected)
There are three typical advantages to wiring the PV for a higher nominal voltage than the battery.
One is that at dawn and dusk, you can harvest a bit more energy from the array.
Two, is that if you have partial shading and the max power point voltage goes down, it is still above the battery voltage. This also helps the energy harvest.
The big advantage, most of the time, though, is that there is less wire loss in the PV to controller lines since the current is lower. This is an I^R relation, so if you double the input PV input voltage, you reduce your wire loss by 4.
Or, ppl can save money for very long wire runs by being able to use smaller wire. Sometimes this is all it takes to more than pay for the MPPT charge controller.
Have a day and 1/2 !
boB