Sion's Q.

I've already said this...but, in the champion spotlight for re-worked Sion, the person talking said that if Q was ever interrupted during its charge-up, you could cast it again sooner, which is seen at around 2:10 in the video. Yet, frequently, I am interrupted during my Q charge-up, and waiting the strike's full cooldown. And this is FREQUENTLY. Does being knocked up by Janna tornado, or away by her ult, not count as an interrupt? What about Rammus's ball form? Or Jax's E? Do these not count or something? Because my last game as Sion, I was pretty much useless because I had to keep waiting for Q to charge, only to be interrupted again, wait the full CD, charge, get interrupted, and then wait. Again. It's getting to be an issue.