Hello Tixan. It is not a bug, indeed. Hida is merely the only inland province with a Sawmill -- thus the developers had the option to either create two separate tool-tips concerning the perks provided by the Sawmill chain, one type for Hida and the other for all other provinces, or to leave it as it was. Doing nothing is always faster; one can't really begrudge it to them, as it is so very minor.