then they would do so seamlessly rather than with a big crease between the blue backgrounds
Excuse me? Do you live in the same universe as us? Colors can change dramtically even across the same surface/object due to lighting. Just go outside and look at things. Unless you have sight impairment, then I can understand why you think everything is blurred together and is all the same color. Three Rings aren't preschoolers who just use the "Fill with color" tool to make their backgrounds.
You are failing to understand
Nope, the example that Feyi provided matches exactly what you just said in that comment. One image, creases across the blue background.
At any rate, Feyi's given hints that they've seen the original image, and knows that all the pieces are from the one image (although not from the image they've seen, the images that Three Rings are releasing are from the concept art, but they still look quite alike and have a very similar background to the final artwork) so you're kinda arguing against solid fact.
You are failing to understand. If the pictures connected then they would do so seamlessly rather than with a big crease between the blue backgrounds. I imagine these are all parts of the same picture, yes?