Is this a Bug on Illaoi?

This happens to me often when ever up against I understand the tentacles from her ult does this but every so often the tentacles from her E have no indicator and are close to instant it says nowhere that the tentacles will do this on the description of her E so why does it happen. Can someone explain?

Disclaimer: i Have no issue with as a champion I am pointing out something that is inconstant and doesn't seem to be written anywhere that says it will do this.