Is the game really so bad coded that they need to make it either ranged or mounted? Making a unit both ranged and mounted should be the easiest thing...
As for the second point, it makes some sense flavorwise, but in that case the unit should spesify it, as I doubt many would see this intuitively. I would also say that pikes are efficient against cavalry in general, as you have an easier time hitting a higher target.
To support this, notice how pikemen get their bonus when attacking too. By your logic, pikes should only get a bonus when defending (fortified?) against cavalry.
From a balancing point, the Keshik isn't exactly weak either, not that it is trully part of this equation.
I still doubt this can be intentional