IMO it makes sense for a magical spell to be able to see through magical hiding, (sanctuary, invisibility) but not be able to instantly pierce non magical hiding aka stealth that was gained over many levels of skill allocation.
As the nwn wiki says, some modules simply give it a boost to spot or listen. I'd like to leave it at just piercing magic hiding, personally. If I remember correctly, there are other spells to boost listen/spot.
My two coppers.
