Geofencing is simply recognizing your location as a condition of whether is feature is enabled or not.
For geofenced charging, you might decide for myriad reasons that are not relevant to the discussion, you do NOT want/need to pull 17-18kwh from your charger at HOME because you're generally in no rush, however, if you are hitting a level 2 charger on the street while running errands and getting lunch, you want it to go as fast as possible.
In short, if you desire the ability to have different maximum charging rates (for L2 only, they're not doing this for L3 as they don't want people clogging up limited L3 chargers) based on WHERE you are, that's what geofenced charging rate selection is for.