The first place my daughter lived in off-campus when she went to college was a nice split level single family house with a very odd room.
It had this HUMONGOUS kitchen/dining area. It was bigger than some NYC apartments. It also had a very large yard. But off this huge kitchen area was also kind of a large room. Way too big to be a breakfast nook. Could have been some kind of planting room, but why would you need that with the huge yard? Not a bedroom, too many windows and there was an little bedroom on that level.
Of course the kids used it as a beer-pong room, which it really seemed to be made for.
At one point the owner had some appraiser come to look over the house. He asked the roommate: what’s that room? She said: we were hoping you could tell us!
Sounds like a sunroom.