>>243715Because she's the only one that doesn't have a 2D model. You might think it makes little difference when they're all depicted on a flat poster, but there's a lot of subtle differences, like it changes the way she's shaded, how smaller, more intricate body parts look like her hands and fingers, how detailed her hair is in comparison to others, and even her entire outline in general.
Surprised no one gave you this answer already. Is my eye for these kinds of things the reason why I was the only one among my friends who thought CGI Grand Moff Tarkin looked horrible and distracting as shit in Rogue One or something?