It would be if using or not using terror would be orthogonal to success in war. War is a zero-sum game and you simply can’t throw out anything giving advantage - you’ll be punished by evolution, as simple as that.
Unless you are in some artificial situation where rules of war are respected and if they are not you are punished by neutral sides. Sadly our era doesn’t have any such mechanism despite all the declarations. It’s not Frederic the Great’s time.