Secondary abilities not proccing when under CC?

So while my team basically dominated late-game just a few minutes ago, I was a little concerned about my stun every 4 casts as Annie. I would provoke the enemy into wasting their CC on me so teamfights would be easy clean-up for my team but whenever I got hit by a knock-up effect or bumped around, or ANYTHING, really...the spells I cast while I had the stun buff active on me would cast, they'd HIT, they'd do DAMAGE, but they wouldn't STUN the target.

Is this intentional or is this a known issue, albeit one with little attention paid to it?

I feel I cannot contribute as significantly as I should be if I have to pray and be lucky enough not to incur CC effects before I cast.. I mean, Exhaust doesn't get affected, neither does Ignite, so why would the whole incentive of building ability stacks be completely negated just from one of the most commonplace effects in the entire game?

Annie is still a force to be reckoned with, yes (I even got full build on her, including boots and trinket, all as a SUPPORT!) but I felt that I should check in to make sure that I wasn't missing part of the story here.

Which brings us to the main, overall picture of a question: are secondary effects on abilities SUPPOSED to handle differently while under CC effects and whether yes or no, what is the criteria that is used to determine how these different interactions play out?