Watching MLB games in person I've noticed most hitters at that level put their foot on or at the back line of the box. It doesn't matter if they are facing a 100mph flame thrower or a pitcher throwing 80mph curves. There has to be a reason the best hitters in the world do that. My guess is they are trying to get a fraction of a second more reaction time.
That being said, DD typically stands at the "middle-back" part of the box with her front foot even with the front of the plate.
Not sure that comparing a 6'-2" man in a 6 foot box with a 5'-8" woman in a 7 foot box is a valid comparison. Baseball players have much less room to move about.