[GAMEPLAY] Volibear W Attack Speed Delay on Level Up

I noticed while watching this video that whenever you level up Voli's W , the attack speed buff does not update until after any current stacks fall off. An example of this is at the 8:20 mark in the video. Voli has three stacks of his W (level 4) and his AS is 1.11. He levels up and levels W to level 5 while his stacks are still at 3. His AS does not change. Once his stacks drop and he gets them back to 3 his AS is now at 1.19. It seems that the attack speed buff does not instantly apply.