What's odd is the document is all about being able to do the complete process using Microchip's MCU, so I doubt it expects another chip.
The input goes into the MCU's built-in comparator, the voltage of which is divided by the Rgs of the lower FET. If the buck/boost is working with a higher voltage it needs a resistor and possibly a zener. Max comparator impedence is 10k, but 10k and ~100ohm (RGS) leaves little for the comparator to do it's job..
Regards,
Andrew