That is something that were in practice, but I would say that it is not at all today. It is (usually) not errors.
Thanks so much for clearing that little one up.
On the topic of Anna Signe, I think i've found the details of her arrival in New York in July 1899 on the SS Hekla (2) part of the Thingvalla line. She arrived alone it appears. The sad part is, the only census that she may have appeared on was destroyed in a fire.