I have 350+ double-sided posters. The chance of my Inception DS original being a fake are about the same as Godzilla arising from the Potomac tomorrow and destroying DC.
Even if someone could create a technically perfect DS repro - and I've yet to see any DS digital repro that comes close to the quality of an original - no one in this universe would take the time, effort, and added expense of creating and printing an absolutely perfect DS repro of this particular poster, which auctions for around $50.
A rational reproducer would do what MovieGoods and Loce do: make a reasonably decent SS repro that can be printed cheaply for non-collectors and sell it for $20. Those repros are not aimed at hard-core collectors, who will instantly spot the fuzzy text/logos.
I showed the fake poster to two of my colleagues today. Neither had a clue that the poster was fake. Even after I told them it was fake, they were unable to figure out why. Even after I showed them the fuzzy printing, they said they really didn't care.
That's the audience these repro sellers are aiming for - non-collectors with a casual interest in a particular movie.
So in the end there's nothing that notable about this particular fake. It's just a typical example of a medium quality repro - exactly like the MovieGoods posters I've seen. The real "tragedy" is not that hard-core collectors like us are being ripped off. It's that casual collectors are being ripped-off.
I'm not questioning your credentials (I own 3-4x more DS and have handled at least 20x, neither of which mean anything except that usually all I need is smell and paper quality to spot reprints - reprints, like a lot of wilding posters, are 'spongier') and I agree with the majority of your post, but none of it has anything to do with my point.
Authenticating is about reducing error and uncertainty. By starting with non-sourced posters as your base you introduce unnecessary error into the equation. In most cases, like Inception, that changes it from 'I'm certain' to 'I'm nearly as certain as I can be'.
I'm lucky in that 99% of my modern posters were personally theater sourced, but I did purchase a poster with a known DS reprint from ebay, under similar circumstances as your Inception. It passes all of the tests, but I still would say 'I'm reasonably certain' that it's an original.