I've seen that as well. The only logical explanation I can think of is that it's a sort of work-in-progress sort of thing, it's meant to train you for the actual king race by pitting better opponents than the king himself against you. The game is lowering the barrier for you by making your life hell earlier on and then seemingly reward you for it at the very end.
It's the same story with all the other kings, except for the drift king. At times he's better than even the player, but most of the time he's on par with the competition you faced to reach him in the first place.
But, when I first went against Ryo for a Grip race, for some reason, I kept losing, until I got a better car.