There is a type of sofa for two persons that has the back between the two persons. In other words, it isn't a love seat; it's more like a twisty, weird set of conjoined chairs. I don't know if this phrase applies to that piece of furniture, but I know they exist.
Yes, some had a sort of S-shaped back, so that two people sitting in it are facing one another. But I think this term is now also used to describe two chairs facing the same way and joined by a small table--lots of patio furniture made this way. Like this.