Yes and no. We have no real confirmation that there is a "realm of death magic" if that is what it means.
And realm and cosmic force while related aren't necesasrily the same. Otherwise you could only use death magic in the realm of death, and the tdeath pantheon would only be able to wield death magic, which theyc elarly wield every cosmic power available.
Is that what it all it means? I think there is a play on words. When you use death magic, you arne't using all the magic of the shadowlands you're pretty much using domination magic only.
What exactly do you think "death magic" means ?
But then anima is clearly described as the essence of the living souls that transition to death. It's a funny way of definign "death magic" ..butI concede you could be right. Anima is the "mana" of that realm. The fuel