Perhaps because the eye glow has no uniform source and isn't a product of either Domination by the Jailer or the Lich King. Generally speaking, eye glows in the Warcraft universe are a product of being in either an unnatural state or the product of channeling a particular form of power (actively or passively). Undeath itself, stripped of Domination, causes many eye-glow type effects: crimson, amber, blue, and even white. There's no real rhyme or reason to it, as it's either purely contextual or a product of multiple influences acting in tandem.