Now that you have discovered Material Zones, you will find that different models will have a rather extensive anatomical definition, i.e., Victoria 4, or simplified, i.e., La Femme.  There are advantages and disadvantages; the more extensively the model is divided, the more cumbersome it is to change all the node values.  However, having a greater subdivision allows you to apply different textures to specific body parts, i.e., tattoos to arms, dirt to hands, make up to face, etc. without depending on a mask layer to isolate those parts.  You posted 3 different models in the comment above, go back and look at the Material Room shaders for each and you will realize that they will have different node arrangements, either simplified or complex.  And depending on those arrangements, you will have varying amount of skin response to the lighting environment.