CompositeThrowable inconsistency?

composite.scala

object Test {

  def main(args: Array[String]) {

    def process(animal: String, n: Int) = {
      if (n % 13 == 0 && n > 0)
        throw new Exception("My " + animal + " hates number " + n)
      n
    }

    def show(what: String, messages: Seq[String]) {
      println(what)
      messages.foreach(m => println(" - " + m))
    }

    def test(u: () => Any) {
      println
      try {
        u()
      } catch {
        case e: scala.collection.parallel.CompositeThrowable =>
          show("Composite", e.throwables.toList.map(t => t.getClass.getName + ": " + t.getMessage))
        case e =>
          show("Simple", Seq(e.getMessage))
      }
    }

    test(() => (0 until 20).map(process("hamster", _)))
    test(() => (0 until 20).par.map(process("hamster", _)))

    test(() => (0 until 50).map(process("rabbit", _)))
    test(() => (0 until 50).par.map(process("rabbit", _)))

    test(() => List("cat", "dog").map(a => (0 until 50).map(process(a, _))))
    test(() => List("cat", "dog").map(a => (0 until 50).par.map(process(a, _))))
    test(() => List("cat", "dog").par.map(a => (0 until 50).map(process(a, _))))
    test(() => List("cat", "dog").par.map(a => (0 until 50).par.map(process(a, _))))
  }
}