Tahm Kench and Yi stun bug

The new champ is unable to stun every fellow bronze player's nightmare, when Yi uses his ultimate. I believe this is because highlander still thinks tahm's q is a slow even though you have the three stacks on Yi.

Steps to recreate 1.Be Tahm Kench 2.Have a Yi on the enemy team 3.Have Yi ult 4.Apply your passive 5.Attempt to stun Yi and be prompted that Yi can't be slowed