The transformation is a situation where the character must pass, it was an experiment that went wrong, embracing this new path will depend on the player, then, for all intents and purposes not tying me to small details, yes, transformation is optional from the moment the story takes shape.
Besides, in some other moments (quests) you will need to become a woman, but that does not mean that you are going to walk the women's path, but only to complete some mission (disguise missions for example), you will not have to have sex with anyone (unless you want). At this point, you just have to look at the skill as a super power of transmutation, nothing more.