∀ {C : Type u_1} (X Y : CategoryTheory.FreeMonoidalCategory C),
  Quot.mk (⇑((X.tensor Y).setoidHom (X.tensor Y)))
      (CategoryTheory.FreeMonoidalCategory.Hom.whiskerLeft X (CategoryTheory.FreeMonoidalCategory.Hom.id Y)) =
    Quot.mk (⇑((X.tensor Y).setoidHom (X.tensor Y))) (CategoryTheory.FreeMonoidalCategory.Hom.id (X.tensor Y))