I realized this does not have Scala collection semantics either. See:

    scala> List(1,1) intersect List(1,1)
    res37: List[Int] = List(1, 1)

    scala> List(1) intersect List(1,1)
    res35: List[Int] = List(1)

    scala> List(1,1) intersect List(1)
    res36: List[Int] = List(1)

    scala> List(1) intersect List(1)
    res34: List[Int] = List(1)