Just because History is not just about dates, armies and economy. There are other subjects that are not necessary related to something that can be represented in games/mods.
I'm not a specialist of the 18th century but have more knowledge about Middle Ages. SSHIP is based on M2TW - Kingdoms.
So, if I write an article about how the food evolved in Western Europe between the 12th and 15th centuries, how can that serve my mod?
If I write an article about how the perception of the Catholic religion by the common French people changed during the same period from the fear of God to something more personal and more focused on the Cult of Mary, how can that serve my mod?
If I write an article about how the art evolved in Western Europe still for the same period, how can that serve my mod?
The argument saying that you can't write something on a specific time of History without serving your mod is flawed.