Yasuo Execute bug (gameplay)

When Yasuo takes just enough damage to break his shield and then dies to turret it counts as an execute. Picture this, Yasuo goes in for a dive on Gangplank, Gangplank q's Yasuo under turret and then Yasuo dies to turret, yet for some reason it counts as an execute. I could not for the life of me figure out why this kept on happening and then I realized it was because gangplank q early game only destroys his shield. This is easy to recreate, just have Yasuo go under turret and have Gangplank q him and watch as it turns up an execute, I haven't tested it on any other champions so I'm not sure if it only happens vs gangplank or not. I have been getting into Gangplank lately, and this bug has happened to me twice in the last couple of days, and is very aggravating because it is 300 gold every time it happens.