∀ (X Y : SSet.Truncated 2),
  (SSet.Truncated.HomotopyCategory.BinaryProduct.inverse X Y).comp
      (SSet.Truncated.mapHomotopyCategory (CategoryTheory.SemiCartesianMonoidalCategory.snd X Y)) =
    CategoryTheory.Prod.snd X.HomotopyCategory Y.HomotopyCategory