Heroes 5.5 WarGame Edition - Tactical Edition.

There was a time when that was the case, but I eventually brought the Knights back to level 6 because they are the main offensive force of the Humans, and in terms of weight class, they are still heavier. But from a gameplay perspective, it's just a small formality, as they are equal.
It's significantly more difficult and takes longer to develop to Knights than to Griffins, which is why in a controversial situation, the Tier was left at level 6, as a more high-tech unit.