When Warwick ult is interrupted he continues to damage the target

I was playing Ashe in a ranked match with a Warwick on the other side. My support was a very skilled Leona who was quick on the draw to stop the enemy Warwick when he used Infinite Duress. He used it on me during a fight and Leona stopped it immediately with her Q stun. As soon as the Q stun landed, I was no longer suppressed, but the damage continued until I flashed out of range. This happened several times in the match.

His ult never used to work this way. When he was stunned, it canceled all effects of his ult, stopping him from dealing any damage even if the initial target remained in place. This unintended behavior might be part of his insane power leap.

Edit: This seems to affect Katarina too. It may affect all channeled ultimates.