Consider the size of Far Cry 5's Fall's End, which seems to be a comparable size to the village noted above.
If you ignore the oversize graphic to denote Fall's End, but just look at the area covered, then the two hamlets can be aligned in size, meaning that Far Cry 6's starter island is smaller than Holland Valley, but not much. Maybe 2-3x larger than the FC5 map.
I'm pretty sure Far Cry 4's map was bigger, but the FC6 island may match the Banapur starting valley, meaning that the FC6 map isn't hugely bigger, but maybe 30% more.
https://www.dropbox.com/s/zzv0okj6b9...6.49.png?raw=1