[GAMEPLAY] Fizz Playful Trickster and Renekton Ruthless Predator

Unlike every other untargetable skill (vlad pool, yi alpha strike, mao twisted), Fizz E can fully waste Ruthless predator by casting it mid animation, but prior to the damage being applied, not taking any damage, stun, using up W buff, be it normal or empowered. Why does it not work like every other on auto spell which either hits or remains/can be used after pole? Coding bug?

To reproduce simply:

1. Open any game
2. Pick fizz with renekton bot
3. Wait for his attempt to w, at any point before the second "attack"/damage hit use Playful/Trickster
4. Notice Ruthless AA buff gone. Reproduced 5/5 in bots.