If this is not a bug, is a terrible mistake. Anivia's Q should work like any other skillshot.

Comparing her to Lux:

If you use your Q with lux and your pointing outside the range of it you will fire immediately. If you use your E and your pointing outside the range you will walk towards that direction untill you're in range.

This is because Q can be interrupted at any moment while E will go through units, Anivia's Q works like Lux's E now and it's very annoying and inconsistent.