If it affected morale, then it would be logical that it wouldn't apply to undead.

No, I was talking about morale separately. Like, it's possible to increase morale for a Necromancer, even though it's useless for his armies.
As for the aforementioned shout, its name already suggests that it's related to morale. It's like it appeals to heroism, which the undead completely lack.

UPD: Does anyone know what this egg is, which pretends to be an artifact, but it's unclear what properties it has. The description says it's a mysterious egg >_<