How do the MAX endstops work?
You should see MAX endstops similarly as MIN endstops, or as an additional option to protect the printer:


Similarly seen as MIN endstops, you would define in the firmware that you are using them to set a reference point at maximum values, your offsets and bed dimensions would be calculated from the MAX positions;
You can configure the MIN endstops and have additional MAX endstops set beyond the bed size dimensions. If the printer would encounter a layer shift causing the nozzle to go beyond the printer (MAX) boundaries, the printer shuts down when the MAX endstop is triggered.