ISTR there was an anti-submarine weapon similar in size to a depth charge that was actually a homing torpedo but for security reasons it wasn't called a torpedo. So presumably the Sunderland could carry torpedoes, they just wouldn't appear on the records as such.
Also IIRC the Sunderland at Duxford was involved in trials to carry 2 Chariots (manned torpedoes) cradled on the side of the hull for launching after a water landing, probably the closest the Sunderland got to carrying full sized torpedoes.