Average journeys are incredibly short, but also not really relevant. If I get a car that can only travel my mean trip distance, half of my trips can't be traveled without refueling during the trip. Even the 95th percentile, as analysed by the linked article, isn't very useful. A car covering 95% of trips still can't make 1/20 trips. The car needs to cover at least 99% of trips, making me refuel only during 1 out of 100 trips. Some people will even demand covering 99.9% of trips.
The borders of an island simply cutting off the long tail of trip distances does a lot to reduce required range.
The borders of an island simply cutting off the long tail of trip distances does a lot to reduce required range.