Alleria isn’t more void elf then the void elf. She do have more void power than the void elf player but her body isn’t as affected by void then them.
Alleria is more like a shadow priest. The void is her class. When she use the void she use it as direct attack.
Void elf player have their body changed by the void. Void isn’t their class. They dont trow bolt of void to their enemy. They barely control it.
The difference is like a orc warlock and a fel orc warrior. The orc warlock use more the fel than the fel orc but is still just a regular orc.