Imagine this: the female model takes a long time to make, with the tit extruding and cloth shading, player rendering, etc. Now, imagine a male model. the models are different, so you cannot just copy 'n' paste a bunch of code pieces.
Posture and chest can easily apply to males. Adjusting this in-game is done with a single command and the result is based on an animation in the model. It is not done by redesigning the model through script. Clothing is also a few quick commands making parts of the model visible and invisible.
The majority of the work is in creating and animating the model and its clothing. The model shown in the image is very early on. Every piece of clothing has to be modeled onto it, then it has to be animated.