Are Death Knights affected by the Sunwell?

Sorry if this has been asked before, but the Midnight campaign has got me curious. While doing the Arator questline, you can ask Alonsus Faol about his relationship with the Light where he says that, as an undead, exposure to the Light causes him pain, just standing outside the Sunwell's building causes him immense pain, and if he stepped into the building, it would destroy him.

However, I'm playing a Death Knight, and I can wander around in the Sunwell with no issues, which I assume is also true for undead players. Is there a lore reason behind some undead apparently having immunity to this aspect of the Light, or is it purely for gampley purposes?