pixelat3d, thanks for the registry work-around - I just tried it and it worked perfectly.
Also, to back up the original poster, I, too remember the very first time I booted up the game it booted into 2560x1080 - looked fine. But I wanted to take a screenshot, then switch to 1920x1080, take another screen shot, and compare - I'm always paranoid about games stretching/cropping the frame rather than just revealing more of it. Anyway, when I changed the resolution to 1920, I couldn't change it back to 2560 - what's more, at 1920 it was DEFINITELY stretching the frame - with full-screen mode on. But when I turned full-screen mode off, rather than putting it back to the normal resolution, 1920, with black bars on the side - as it should - it would give me windowed.
TL;DR: I, too, noticed that 2560 disappeared from my first use of the game, and am happy to have a way to do it in 21:9.
All that being said, has anyone done 2560 vs. 1920 comparison shots? The game looks fine to me, but there are certain cutscene framing shots that seem off - where it feels a bit too tight on a character's face, or where there's something on the far left and far right of the frame that seems important and that, in 1920, would be cut out - thus leaving me to wonder, if I WASN'T using 2560, would all of this important detail be cut? i.e. Zoe and therapist being on opposite sides of frame in some shots - it's fine in 2560 but would be cut out in 1920, assuming the game is rendering and showing us more rather than less.
Anyone have any thoughts on this? Thanks!
In this 2560x1080 shot, if I didn't have it in the wide aspect ratio all of Zoe's head/hair would be cut out, leaving the therapist looking into blank space - clearly we're meant to see PART of Zoe. Does this mean I'm seeing more than a 1920, or the same, in which case how is it being cropped?