Jesus was a true descendant of Mary. Otherwise, since he had no human father, he is not a member of the human race. Only a true son of Adam could stand in as a substitutionary sacrifice for other men. Only a man could intercede for other men as a priest. And, finally, if Christ has no human ancestry, then he cannot be a son of David and has no just claim to be "king of the Jews," and he lied.
Theology matters. And sometimes, even the seemingly fiddly little details have huge implications.
If Christ prexists with the Father how is he created in Mary’s womb as a new creature?