I wouldnt say less than 1/3. Buildings look about 9" wide so line them up along one board edge and add the tree bases on as well and your almost at the magic 33%.
Where it differs is that most of that is taken up by big bulky buildings instead of walls, rocks, cliffs, bushes and all the other detritus that makes up most other boards. You end up with a really open board rather than one with very tight lines of sight and lots of things to hinder movement