I think the point of the island is to show that when you have limited space, residential density really matters. Even if you took away all the concrete, spacing, etc between houses in this example and just out 100 ranch style homes in a corner with no spacing in between them, it would leave room for significantly less nature.

Your neighborhood sounds beautiful, and that's great, but that ratio between nature and residents is probably being achieved with more land than if high density residential housing was in place.