Build Default is Realistic Game Mode. Personally I have no objections if the world scale is different between Arcade, Realistic AND Iron Man.It would be nice if there were an intermediate scale between the two, with the islands 2/3 the size of the normal map, about twice the size of the islands on the open sea map. This wouldn't be bad for a default normal map, either.
I imagine most Arcade players will not be big users of DirectSail, so having the current situation in use there should be fine.
But on Realistic, it would be good if DirectSail uses a scale that is sufficient to not cause silly bugs like on the "too low Arcade scale".