Why? Literally the most creative control they had was looking at the Gen-AI output and checking it before slapping it in the game, and they either didn't know or didn't care. Either way it was perhaps the most singular act of intent in the entire creative process, because the Gen-AI can't comprehend shit.
Want more? The third image, the girl in the white dress? Ignoring how the background is nonsensical garbage with hallucinated lines and details all over the place; the girl's ears are not level, despite her head being so. No idea if this was something on purpose, something wonky in Koikatsu, or yet another hallucination created by letting the Gen-AI off the leash. Maybe because the model was given carte blanche over the head in the way they weren't over the body, because the body is still obviously a 3D model.
How so? That plunging dress should be just that; a dress. But in Koikatsu, all of their clothing is split into upper and lower sections. A product of the game, allowing you to mix and match pieces to create custom outfits. Works well enough for a t-shirt and jeans, or a skirt and blouse; but it also means that things that should be one piece now have a seam at the waistline caused by the fact that it is two separate 3D models pretending to be a single piece. Typically the cell shading of stock Koikatsu will mask it a bit better, but the image-to-image picked up that seam and ran with it, making it even more distinct and visible in the final output. An output that, again, the dev looked over and approved of before slapping it in their game. They could have noticed it and photoshopped it out, but they either didn't know or didn't care; and neither option is great.
This continues down to the hem of the dress, where it bends funny instead of draping naturally according to the curvature of the legs and gravity. Why is it doing that? Because Koikatsu doesn't use cloth physics, their clothing is hard weighted to the animation skeleton. So that means that dresses and skirts are made by having the model vertices (the points of the triangles that make up the model's polygons) follow the legs. This results in parts of the dress being stuck to either leg and moving uniformly with them, and a really unnatural connection between the two sections that only become more visible the more the legs are pulled apart from being perfectly parallel. So having her in a pose that favors one leg, causes the model the look funny; and now the final image has an artifact of 3D modeling in what appears to be an 'original' 2D image.
But again, checking over the final output before slapping it in the game is the most control any human has over the Gen-AI process, and it's clear that they abdicated their attempts at quality controls. If the Gen-AI couldn't fix it, they sure as shit weren't. Remember that fixing mistakes requires knowledge, effort, and care. You need to know it was a mistake, be willing to put in the work to correct it, and finally care enough to do so. Evidence indicates they're probably lacking all three...