Uruka was probably the most unlikely pick. She wasn't one of the two original geniuses, and it's neither Senpai nor Mafuyu-sensei.
Oh well, if that's how it is, I guess it's the way it has to be. I'd say though, she's a very solid pick for a long-term relationship. Well-rounded character with no glaring flaws that might make life hard (like Rizu or Mafuyu).