I theorize that the "ph' the Stephanie is due to it being the common Greek "Double ff" However the male rendition of Stephen said Stee-Ven is due to the Gaelic influence of the British Isles and is "ph" only bearing one voiced F like in the word OF said "uV" The dominance of the name Stephen said Stee-Ven influenced Stephanie to share in the short Steve or Stevie.