I've worked for Intel for 11 years, before that I interned with Inmos Corp. Mostly I've done design, but more recently I have been working in "back-end" debug for several years. Among other things recently, I've been writing tests for the burn-in ovens at Intel and looking at burn-in fall-out (why parts on a product are failing in burn-in) and analyzing large volume burn-in data (literally hundreds of thousands of parts). This is microprocessor burn-in - high temperature, high voltage testing done to try to eliminate "infant mortality. I am about as close an expert on this subject as you are likely to find posting at Anandtech and I'm the author of the FAQ entry that was quoted above.
Note that I am not speaking on behalf of Intel - I am not an Intel company representative - nor is anything that I'm writing specific to Intel CPU's... all CMOS circuitry from DSP's to ASIC's to CPU's all are like this.
I do not dispute anything in this thread. But what I will say is that this burn-in effect is not affecting anything on the CPU die. The silicon is not speeding up. Whatever effect you are seeing, it has nothing to do with the microprocessor silicon speeding up. In burn-in on CMOS circuitry (high-voltage, high-temperature operation), the transistors will always slow down by a small but measureable percentage. NMOSFETs slow down due to impact ionization creating trapped charges in the oxide of the gate shifting the Vt upwards. PMOSFETS slow down to PMOS BTI creating positive charge interface traps at the oxide-channel boundary which also shifts the Vt and reduces saturation current.
Beyond that, if this technique for burning in a part seems to help, then my only input is that it's not the silicon speeding up. I don't see the technique as posted by the OP as doing any harm. If it helps, then it's a good thing. About the only negative thing that I can think of is that running at an unstable operating point could lead to data corruption on the hard disk which could result in data loss (ie. your hard disk data is lost) but this isn't likely... just a possibility.
Lastly, my company email is in my profile. If anyone doubts that I am who I say that I am, email my Intel email address, and/or do a search for "Patrick Mahoney" Intel "Fort Collins" in Google.