Yasuo Shield ignore's turret shot and executes

As clearly Identified in the video, I am playing as Riven and I am dived by a Yasuo. He ignites and E's to me but is clearly knocked up by my Q. Then as we both die I realise that it say's that he had executed. Both I and he were confused. I am going to assume that it is something to do with his passive shield as it goes down as I knock him up. I'd love someone to look into this. https://twitter.com/TerrorCS/status/944713712031666178