The TDP iso chart tests are just what we want for comparing the 70-200 mm with a 2xTC at 400 mm with say the 100-400 mm at 400 mm. But, the pair you show compares the 70-200 mm with the 2xTC at twice the distance from the chart as the same lens without the TC. What we also want to know is it worth using a TC compared with the native lens. To answer this, elsewhere in the TDP site he compares the same lens at the same distance from a target (a flower) with the lens plus 1.4xTC and 2xTC. In each case, the image without the TC is rezzed up to the same pixels as with the TCs, and the TCs give better images.
I have done the same tests with my 3 TCs and a variety of lens. For the 300 mm series II with the series III TCs, the combos are better than the rezzed up native lens, just as on the TDP site. So, I use the TCs whenever necessary. But, for the 100-400 mm, the addition of a 1.4 TC is no better than rezzing up the native 1.4x. So, I leave the TC at home for that lens.
Now do you see what I am getting at.