It sounds like a job for... the WBTA!
(coming soon:
www.wbta.us )
Obviously the internal diode is placed inside the Intel die to serve its own purpose: to protect the CPU, not to let you know your CPU temp. Since Intel doesn't really care for people to know about a measurement that's more to the point (the hidden diode), they let you see the other diode that they conveniently attached away from the hottest spot.
The solution is to perform a test with a heat die. The problem I still have is where to put the probe within the die (pHaestus: did you get my pm?).