LeBlanc Passive Glitch (GAMEPLAY)

I'm attempting to learn Yasuo at the moment because he's incredibly strong as a carry and with the release of a skin riot probably has little intention of fixing him soon. That said, I was against a LeBlanc, and twice I thought I had her. I got my tornado, was ready to ult.... and.... No knockup. She blipped, popped her passive, and the knockup didnt go off. I know it hit her because the tornado damage caused the knockup but the knockup effect was never applied therefore she simply turned and killed me since i couldn't ult to finish her. This happened twice.

If I had to describe how to reproduce the problem, try and get LB right above clone health and hit her with a Yasuo tornado, to see if it produces the CC or if her passive counters it.

If this is a known countermechanic and I just don't know about it that's cool too but it seems like more of a counterglitch so I thought it was worth a post. Thanks.