Yesterday, I decided to play a duel between Sanctuary and Stronghold against a medium AI, and right away, panthers rushed in, dealing significant damage to two units. Then, harpies took someone out, followed by centaurs dealing a lot of damage. And only then did the units from Sanctuary start moving. What's going on? After all, Kirin have the highest initiative; they should be the first to move.
You probably played against a mage – orcs-mages have a passive ability that increases the initiative of their units by 5% and reduces the initiative of enemy units by 5%. So, that's the reason.