Right. This is true because when the PV modules are hot, the MPP voltage may be
at or below the battery voltage. If below the battery voltage, a boost converter
rather than a buck converter might be in order. Right AT the battery voltage,
a relay would be best since there is ~some~ voltage drop from either the MPPT
converter or even a PWM controllers MOS-FETs. (less than a 1 volt drop if done right)
If the PV array is wired for say the next higher nominal voltage than the
battery, the MPP Voltage will always be above the battery voltage. However,
in this case, all else being equal, and not taking PV to controller wire
loss reduction into account, the controller will actually be less efficient
than if its input voltage (PV) was lower. (closer to the battery voltage but
higher than the battery voltage)
It's still typically better to wire the array for a higher voltage than
the battery voltage and use an MPPT controller. This can help when the array is partially shaded too.
boB