Okay, so this is where you're getting hyperbolic. The expo bomber model is not a mock-up. It's an intentional display model based on the film resources done by an extraordinarily talented modeler named Alex Hutchings. Since you're going to be pretentious about getting facts straight, it's time for a little info dump on something you seem to know nothing about: the art direction process. Concepts obviously start with script needs, and then progress to their concept artists. James Clyne (my personal fave, and the one responsible for this design) and his coworkers then work up a bunch of concept sketches. When a direction gets approved, a first pass concept model is mocked up (by either Neil Ellis or Alex Hutchings), which then returns to be fleshed out in detailed 2D studies (if again, approved) and then proceeds to a final model. This last, in this case, was done by Alex Hutchings. When he's done, this physical plastic and chemiwood model is handed to the 3D modelers to make a digital version.
And it can be categorically stated that the expo model is more accurate than FFG's because A) every comparison of proportion and detail just shows this, whether it's from Incredible Cross Sections, the Visual Dictionary, the Bomber Command book, the perfect side view from the trailer released 8 months ago, the image you yourself posted (and a fairly cursory glance by a trained eye would tell you this); B) it's literally the source material for what the bomber looks like; C) FFG did in fact make many mistakes - they do it very frequently - and LFL literally cannot make any barring internal non-rationalized discrepancies, because they define what this craft looks like.
I think most people, yourself included, don't realize how hard it is to translate 2D imagery to an accurate, proportional, scaled 3D model. It's hard, and I don't want to understate that it requires a ton of effort. I know, because art direction and 3D modeling is my profession, and I've been doing it for fifteen years,along with scratchbuilding physical models. It's as simple as this: FFG rushed the model out without proper source material. Having a ton of concept art for this ship in hand, I can also tell you that the FFG model does not match earlier concepts for this ship, either.