Miyazaki himself has stated that the story and lore of DS games came about on how much he loves western mythology (hence the references to many ancient Norse stuff in the game , albeit with different names ofc) and his own inability to completely understand the english texts on it , so he basically filled in the blanks with his own stuff. Overall , as far as being a theory about the lore , its ok , albeit a bit too loose (people love thinking about vaginas and apperantly everything needs to have a sexual symbolism, when its just a door or a cavern entrance) . The idea of huge enemies with huge swords representing phallus and "castrating" you while guarding the "vagina" (an entrance) is fucking ridiculous. Nice effort tho, but as far as intention from the author its far from what it actually is.