@riot Anivia Bug or working as Intended?

Question for any rioter or anyone who might know this answer. I just had a match as Anivia and I noticed that any form of movement CC (knock up/knock back) canceled her ult. Her ult isn't a channel, though. So, is this intended or a bug on her part? I'm thinking it has something to do with her passive if it isn't a bug, but I'm not sure.
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