These girls are smooth
Also, Probe girl, her Alt, and the tank girl aside, the other girls are what? Flesh and blood or moving resin? To be precise, if one is to cut them open, what will one find? Blood, guts and flesh, or just a solid mass of figurine matter?
They can eat and drink, there is a biological function. But several chapters back, the plot seems to suggest that while they are moving, eating and drinking, they are still physically some sort of figurine.