You would be suprised how little you can change after a gender swap.
Ever notice all of Shirous clueless character traits? His brilliant cooking? How hardworking he was?
Wouldnt they have been endeering in a female character?
I think the only major change was Shirou opting to fight instead of Saber. They probably just importated the origonal script for the scenes of them deciding to fight together into UBW though