[GAMEPLAY] Is this a skillshot bug or what?!

EDIT 2 - i'm stupid and i didn't even say what is the bug - when Lux snares someone before they dash/jump/alpha strike etc they are ensnared and still use their ability... I don't know if it's supposed to be like that but i've seen too many people explit this... This exists for some time and no one cares to tell me if this is a glitch... Seriously why does Lux have a cage if it can't even stop a wild Yi? Steps to recreate -Chose Yi and Lux in the opposing teams -Use alpha strike while lux uses her q (just as the skillshot touches you Edit: watch from 0:50, sorry for quality