God does not live within the confines of our logic. By those standards one would say:
1)Prior to modern medical technology, all pregnant women were non-virgins
2)Mary was a pregnant woman
3)Therefore, she was not a virgin
You are dealing with the supernatural, not the natural. It doesn't fit into the nice neat little package A8 is trying to make it fit into.
*************
With regard to your first assertion, is it not both the natural and the supernatural? I think you may want to revisit A-8's argument. It is as perfect a statement addressing the issue as I have seen here.