Rylai's Slow Visuals and Hiemer Turrets

There's seems to be a weird interaction with Hiemer turrets and Rylai's that I noticed yesterday in game, where it applies the slowing effect but doesn't apply the unqiue Rylai's visual where your champion turns a white-ish color.

Is this a bug or was this done on purpose? (Unfortunately I don't own Heimer, so I didn't have the luxury to test it out in a custom game to see if this happens every time or just that game.)