Seleukos_I. is right about this. If we wanted the map to span as we wanted it then the Iceland's inclusion is more of a by-product of that. The span's criterias:
South-East to include whole Arabian Peninsula and north to include whole Baltic sea (land between finland-sweden). Resulting map includes all of Sahara and Iceland as bonuses. Western border was adjusted in order not to cut the Iceland nor Sahara in half or something like that.
Such info would be part of Map generation blog should you people vote for it.
EDIT: Thinking of Sahara of wasted space and desert is a terrible mistake :-) I think you will be surprised how lively and interesting it's gonna be in DotS (as it was in fact in the past).