Okay, about the IHS vs die readings... If we look at the real world applications, there are so many bad IHS to die interfaces on processors these days. There are people who get strange temps because of these poor interfaces. I'd rather measure from the die for this reason...
Think about it... Does it make sense to measure the middle layer when we actually want to know how effectively the bottom layer is cooled?
Excuse the crude paint drawing...
Would you measure the item that generates heat or just a layer the heat transfers through?