Kalista GA Bug or Spectator Bug?

https://www.youtube.com/watch?v=H4tN0GS721A&feature=youtu.be Just watching some of my friends play league and all of a sudden i noticed Kalista was still auto attacking write when her GA popped. As you can see (if you click on the youtube link at the top), Kalista keeps on attacking Olaf but Olaf is unable to attack back because of the invulnerability of GA. You also notice Heimerdinger's turrets are also not reacting to it either.