[Gameplay] Karthus R targets untargetable champions ( in this case Vladimir in W) when he is alive

Hello summoners, I tested this bug with a friend and it seems to be that when Karthus is alive and ults you he will deal damage to Vladimir in his pool every time, and when he uses ult while being dead he doesnt hit Vladimir in his pool. I have video evidence of live ranked games and custom aram map gameplay if someone is interested.

Regards

Edit: I figured that a video would bring the message across better https://youtu.be/zx5cDUjIK8Y pls excuse the quality