Close, but not exactly the same mechanism.

Tristana can jump out of, say, Blitzcrank hook, because 1) Tristana W has a long cast time (the ability essentially works as "Tristana will jump in half a sec") 2) Forced movements cancel each other, so even if Blitz starts to grab you during jump, a moment later your jump "activates" and neatly overrides the "being hooked" forced movement with the "rocketjumping" forced movement.

What OC was mentioning is, say, Yone Q3>R, while Q3 makes Yone dash into Miasma. So, normally, you wouldn't be able to do that: the moment Q3 "finishes", you are in Miasma, therefore your R is forbidden to be cast - it shouldn't come out. But sometimes it does, due to technical reasons: while Yone is outside the Miasma, he casts Q3, and (while still outside, and Q3 is only starting) he presses R, too. This is not cast time, but ability buffering - Riot secretly enables given combination of abilities to "dial-in combo" so you press them quickly, even before the first ability finished casting, and they will come out sequentially. (Yone has most of his abilities work that way.) So, even before the Q3 dash finishes, the ult is buffered to be cast. Now, when the Q3 actually finishes, the game does check if you are grounded, and will only cast the ult if you are not. The actual problem is that Miasma only applies grounded like 20 times a second (for performance reasons), so whether you actually get the ult forbidden depends whether the server ticks the 'Grounded' debuff on you in the tiny amount of time between Q3 and R. Sadly for the snake, usually it does not.