Heroes 5.5 WarGame Edition - Tactical Edition.

Let's give griffons to tier 6 and knights to tier 5!
It's absurd, but somehow logical.

As I understand it, knights are originally placed on tier 6 not because they are cavalry.
You can notice that human commanders are also, in essence, just guys on horses, but according to the balance, they can take down a dragon with one hit if they level up.
That is, the point here is more about how well-trained this type of unit is (with a fantasy twist), and the presence of a horse is more of a consequence.
In this whole story, I was more concerned that such "commandos" are not available in all factions, and somewhere they are replaced by non-humanoid creatures, as if they cannot train their "commandos" to the same level.
By the way, I consider swordmasters in the seventh game and Clash of Heroes to be strange for the same reason. Apparently, the idea came from the second game, but it seems that the developers simply couldn't come up with normal fighters for humans again.