Brittle Not increasing CC Duration

I was watching a replay of my Ornn gameplay, and it does not appear that brittle is having the expected effect. I had 2 enemies (ashe & Rakan) side by side in game, and used my Q,W,E combo. The brittle debuff from my W only reached the Ashe, and the debuff showed above her head. When I dashed used my E into the pillar, both the Ashe and Rakan were knocked up at the same time, but the duration of their knockup was the same, if anything the Rakan came down first!. The brittle debuff was consumed by the knockup. I expected the Brittle debuff to extend the duration of the knockup 20%. See the replay in slow motion.