I suppose another way of looking at it is with 58 & 78 is that you can combine them to make a long valley between them for those "Head them off at the pass" Blazing Saddle scenarios that you have always wanted or a nice Yugoslav mountain ambush of the supply convoy, you know the supply convoys that always have a Tiger tank (T-34/85 tarted up) as escort.
What have we now as official boards? 1-76, 78-83, 1a/b-9a/b and p-z for 76+6+9+11 for 102. While my previous paragraph was being a bit facetious, a second long thin ridge will not go too far amiss amongst those. You could say something similar about 79, it's not that we don't have a few river boards already, 7, 8 and to a lesser extent 40 and 23.
I do agree that the Fort style boards add variety, but they really only stand out because of the limitations of the long boards. If the Fort ones were the standard we would be going "ooooh!" at the long boards. Long live all boards and the mix!