Right. In the case of Germany, for example, the much admired multi-member proportional system in that country was adopted because of the fact that the Allied countries at the end of World War II imposed it on the country. There was no input at all from the German people, either by referendum or other means. In the case of Ireland, their system of STV was imposed from the outside by the British when they were leaving. In the case of Scotland and Wales, it was similarly imposed through a process that cannot be said to have involved the representative bodies of those two jurisdictions, which didn't exist at the time.
May I take it, then, that a referendum is in fact at least as legitimate a means of adopting proportional representation or considering it as any other method?