Their edit looks so much worse than the original image. Aside from the obvious fact that fattening up her butt is sexist and shallow, her butt being so glossy does not fit in with the rest of her clothing. Nor does it fit in with the theme of her walking through a dirty, dusty nuclear wasteland.
Every one of those Bethesda game mods looks so horribly and distractingly out of place in these worlds, yet the same people using them definitely have opinions about "ugly" characters breaking their immersion.