Because you can never have enough oooooooze!
This creature is essentially an undead ochre jelly that can create zombies from people it kills, for some reason. And command them in spite of having Intelligence -. To be honest, I prefer the template version of Vampiric Oozes from Silverthorne Games, myself, but that's just me.
Orogs are the opposite of ogrillions, being the result of a union between a male orc and female ogre. For some unfathomable reason, this combination of Intelligence-penaltied species results in a creature that has a base Intelligence score of 10, just like humans. Why?
...I'm not sure, really. All the other traits of the orog fit, like a powerful Strength and Constitution bonus and a penalty to Wisdom and Charisma, but having an intellect above the average of both of its parents stumps me. I guess you could explain it as a fantasy version of hybrid vigor, but that doesn't quite fit. ...Hmm...
You know, actually, I may have an idea. What if, rather than the sages' suspection of ogrillions and orogs being the results of gender-flipped mated pairs, they are actually the progeny of different subpecies? Perhaps the ogrillions are your bog standard ogre-orcs, while the smarter, militaristic orogs are part ogre mage?