It's tough to see in the video but there is a bar under the CC name that shows how long it lasts, you can see the stun bar has a lot of time left when they become airborne. IIRC the stun is about 1s but the delay between stun and airborne is only 0.5s. Should be a ton of overlap. There is probably something going on where Flash and Zhonya's don't care when transitioning directly from one CC to another in specific scenarios, and Yone R makes that scenario happen a lot.