But if you were to run two of these in parallel (like in the group test) the microprocessors will be out of sync as to their internal state, because their xtals run at different frequencies. And the internal state of the micro's correction algorithm affects the output data!
So for the group test to be valid you need to sync every micro down to the exact state (sync them to the same program instruction) then the data can be correlated.
Otherwise (as I said earlier) the group test would be MUCH better just using the direct output of the analog comparator after the noise source. i think the guys relying on these tests don't have much knowlege of the internal workings of a seeded RNG and really don't understand the issues... Anyway, that's just my opinion.