I don't know about Norway, but in Denmark, the government wanted to switch from the patronymic system to the surname system, and the people living in the cities did that, but those living in rural areas were more resistant. My grandmother's father's name was Christen Pedersen, and so my grandmother was Jensine Christensen in the patronymic system, which she always used for her name, but we sometimes find Jensine Pedersen in the census records because they used the surname system. I defer to the birth record in these cases.