Vitality Creation doesn't work with Graveyard. 1. Have units with vitality creation or equipment that grants it 2. Spawn units from a graveyard Observe that your units don;t get the 2 HP increase
That's working as intended. Graveyard spawns skeletons, it doesn't summon them. It is one of the few sources of real champs FW has left for Death Benefit.
Graveyard spawns a champion not summons. You can see that the Grave Warrior does not have the summon condition.