Nonetheless, the point is areas built before observation / exploration XP went in tend to be the ones that don't give any/much, especially if they haven't been updated in the past few years or the original author isn't on the staff anymore.

It's up to the author to decide whether or not the NPCs and objects in their areas give XP, and how much (within reason, of course), so it's quite possible Scar simply doesn't want Hell to give much and it isn't a matter of him having not gotten around to updating it.