Because it was thrown together by a designer with precious little knowledge of astronomy perhaps? I don't think most people realise that the Milky Way is a barred spiral.
Considering that the previous trilogy had considerable attention to detail regarding astronomy, I think you can rule that out. First off, they already HAD a galaxy map from the previous game. Second, I find it hard to believe that a designer creating a sci-fi game and specifically an image for a trailer that would be shown to the public would not possess the extremely general (like seriously fifth grade level) knowledge that the milky way is a spiral galaxy.
In the prior trilogy, they actually paid attention to stellar mass, somewhat realistic astronomical distance, tidal locking of planets close enough to their parent star, that habitable worlds around red dwarfs would be tidally locked, that gas giants and ice giants are two distinct classes of planets (and they paid attention to the criteria foe that too), that Earthlike worlds can exist only within a narrow range of temperature and pressure, that gas/ice giants do not form within the Frost Line and thus either migrate inwards or are extrasolar captures.
I mean, sh*t man, I didn't even list HALF of the real life astronomical science that they paid attention to- that's impressive. Yes, they often half-assed or got things wrong, but that is still better than literally any other sci-fi game I can think of.
For those interested, read my most recent post in the Andromeda thread to see the four reasonable possibilities for the appearance of that image that fans have come up with so far. Some, like the "dark energy destroying the Milky Way" ideas are particularly curious.