Total war has also had this issue since Shogun 2 total war. It's as if they're afraid of wide open spaces and want every province to be accessible to another by a single route. In shogun 2 they could kind of get away with it because much of japan really is like that, but in Rome 2 and onwards it was just silly, with contrived impassible forests and hills cutting provinces off from each other.
Shogun 2
Rome 2 (most of the map is like this)
I genuinely laughed when I saw the bannerlord map for the first time, just like total war it has all these short fat mountain ranges with no rhyme or reason to them, and they take up the entire map. I can't think of any reason for this other than a misguided, lazy "it will create choke points for the player" mentality.