Annie - Tibbers Warp Bug [CHAMPION GAMEPLAY]

During a game as Annie, I sent out Tibbers to stall against an opposing Xin Zhao after he nearly killed me. I wasn't watching him after that, but Tibbers teleported back to me (assumingly because he went out of range), and I saw the animation of Xin Zhao's ultimate appear over Tibbers which killed me as well as Tibbers, although I was nowhere close to Xin Zhao. I'm guessing that area-of-effect spells that hit Tibbers just before he teleports back to Annie will also hit Annie. Is this intentional or is it a bug?