Gangplank is supposed to be a very strong split pusher while still impacting the map with his Ult.

So if he can set up 2 or 3 barrels to destroy minion waves insanely fast while farming up his Q and putting pressure on the map. Why exactly must his passive work on turrets? Just seems like an obnoxious strength to a champion that is one of the best at split pushing while also being incredibly impactful with his upgradable global ultimate. He shouldn't be able to use his passive on turrets, while also clearing waves and getting another refresh of that passive to use on your turrets.