It is helpful to visualize the initial penetration between contact pairs.
I agree, but the problem I am having is that I have no detailed information of how CalculiX doest it. I think the penetration in CalculiX is computed based on where the spring contact elements are created. And this is not the same as I would do it in PrePoMax (between nodes and faces). So there would be a difference between penetration computed in PrePoMax and penetration computed during the analysis. And that would be misleading to the user.
OK, the penetration between nodes and faces can still be helpful to avoid some unwanted contact behavior.