[Gameplay] Cassiopeia : Miasma does not disable Ezreal Arcane Shift to be used

Issue On Cassiopeia, when the summoner uses W "Miasma", Ezreal E "Arcane Shift" ignores the following Miasma effect: prohibiting the use of Movement abilities (refer to the video I enclosed).

How to reproduce the issue

1. Summon Cassiopeia and Ezreal
2. Cassiopeia uses W "Miasma" but Ezreal is not targeted
3. Ezreal start to move inside the "Miasma" spot and once he touches the spot, uses his E "Arcane Shift"
4. Ezreal used his movement ability even if he was not supposed to

Does anybody can confirm this is an actual issue and not a "timing hazard" ?