[Gameplay] Gangplank Barrels Do No Damage?

I was recently in a game with a friend of mine who was playing GP top against an Aatrox. I had backed so I was watching an exchange between the two. Aatrox jumped almost into the center of a barrel, which GP detonated shortly afterwards (not a chained barrel, a single barrel point blank, and the animation did go off as Aatrox didn't attack it), and he didn't take any damage at all. It wasn't damage that he took and healed back up, he flat out took no damage. I don't have the new client so I can't post a replay, but I was wondering if anyone else has noticed this? My friend said he had noticed it several times throughout the game, also on Karma (Order of the Lotus) and Xin Zhao (Dragonslayer), but I didn't see it for myself.