He's not measuring TDP directly, he's measuring the difference between TDP of two different processors. The test setups were identical except for the processor.
Again, TDP is NOT peak thermal dissipation.
No. Different manufacturers use different definitions of what a typical load means.
> If not, how would you attempt to test it other than placing the processor under heavy load?
Well given that Intel has stated, "The TDP is not the maximum power that the processor can dissipate." Then testing under heavy load is most certainly not correct.