iirc, regions that had that text gave a +1 exp bonus to units of that type that were recruited there. Both the feature and the way it was displayed (the text used) were quite neat I thought, as it gave different regions a bit more 'personality'. For instance, when playing as the English, I would try to recruit all my longbowmen from Wales (for the +1 exp bonus), even to the extent of being a bit short on longbowmen at times, while I waited for Wales to churn them out.