Tristana jumps while airborne
- You can't use spells while in CC
- If it was already casted Airborne effects interrupt dashes
Normal. Not a bug.
It is.
No, it isn't. This has been in the game since forever ago. It's part of Riot's spaghetti code.
Displacements like airborne are NOT crowd control debuffs, many champions like trist have SELF displacement effects so lots of INTENDED interaction here. If you will notice on the screen while she was jumping she was briefly stunned during part of the duration of her jump but naturally it wore off before she landed so she could continue as click to movement as normal.
The jump is considered as dash and displacement effects interrupts a dash, that's why e.g. Thresh Flay can interrupt so many "jumps".
The Tristana buffered her W so that she took the CC while the spell was casting and the movement of the jump then overrode the airborne effect. It works the same way as when people QSS/Cleanse a knockup the Flash out of the air.
A knockup/knockback has two components - a stun and the airborne effect. The airborne effect can be overwritten by movement abilities, while the stun prevents champions from using said movement abilities. By cleansing the CC and flashing or buffering a Trist W/Ezreal E you can effectively ignore the stun and override the airborne effect.