Technically speaking jerf, that was Merlin who gave Artoria male genitalia. On the subject of Mordred, Mordred's a homoculinis so she looks like Artoria, it's complicated but that's the gist of it
I imagine Kouga wrote the story and gave Minakata a discription of the main characters got back the art as a big group of the girls just kissing and made lemonade with lemons.