I read a post by the author of Core temp. He explained a bunch of that and the fact that neither Intel nor AMD will give any info on what the readings of the DTS actually mean. They have to try to figure it out. I always thought that the DTS told how far you were from TJMax, so if you know what TJ Max is and how far you are from it, you can come pretty close to actual temp. But, maybe not.
I guess, if one of the 1155 pins in my CPU socket read the T Case, the motherboard would know. I read on the ROG forums that the AI Suite read Tcase. It either does or is way way off. It can give temps 20 - 30° lower than core temp, real temp or any other program.
Why Intel or AMD won't release that info is beyond me.