It isn’t really fair to include Macinaw Island because cars simply aren’t allowed on the island

I don't see why not. Its that rule that makes it so and they could get rid of it at any time. I mean just because they are ahead of the curve. I feel my downtown should get rid of cars for the several square mile city center area that has all the museums and such. If it did would it be unfair to include such a thing in its bike friendliness score? I mean its laws that mandate the bike lanes.

It is very difficult to live on Mackinac Island, it is 100% a tourist town. Its like saying Disneyland is the most walkable city in the US.