Gangplank Powderkeg bug

...how is this a bug?

You want GP to give your team's marksmen either a ranged 400 radius crit with 60% armor penetration, or have the barrel completely wasted by ally attacks?

Edit: I mean, GP allies shouldn't be able to attack the barrels, but barrel may have been treated as a neutral minion for the ability to function as it should, and the invulnerability to ally destruction is just band-aid fix to a possible problem.