First of all, thank for your feedback. :)
In my case, the answer to your question is pretty trivial: Their Eyes has a true low res of 320 x 180, unlike other games that "simulate" that resolution just by drawing big pixels (take Minecraft, for instance). Therefore, as you rotate the rifle, it is automatically redrawn to match the angle: the pixelated effect is retained, but the drawing itself is pretty messed up - as a result of an automatic process.
Enter the Gungeon, on the other hand, looks as the result of a much more accurate work. It doesn't matter the angle, the drawing is always pixelated and always very aesthetic: maybe I'm wrong, but I would say each gun has been manually redrawn for each fraction of 180 degrees and then just mirrored to complete the circle.