The thread you have used as "evidence" of a thread with the "big GTR boys" proves nothing to aid you unfortunately.
All it proves the turbo's are identical.
The GT-SS's are identical to the Garrett -9. Have you even seen GT-SS's part number? I have, given i own a set.
It's 707160-9 - What is that the same part number as I wonder?
There are minor, and I stress the word minor, differences between the GT3071 and the 2835.
Now, the discussion here is the GTX3071, which is going to better turbo than the GT3071, Garrett have shown it to be such already via the compressor maps.
To say they are outlandish statements is a bit ignorant. The results are different yes, and they are minor. Does it attract the price tag difference? Thats upto the owner.
However now with the GTX3071 on the scene, the general consensus is that the 2835 'premium' no longer applies given the GTX3071 will be dead on if not infront even with the off-set housing sizes. Obviously results will prove this either way, but this isn't a new Billet/Precision turbo where no-one has seen any info. We already have the GT3071 to base things off.
What you also seem to not take into account is an external factor. The 2835 carries a hefty price tag and people purchasing such a turbo generally have the best of the best given cost is clearly no object for their aim.
This can, and most certainly will, have an effect on end results.