Quickcast and Range Indicators help please

So I have been using Quickcast for a long time now and I have always seen streaming where players can display the range indicators when holding the key down. I have done investigation and found the "Display Range Indicators when quickcasting" toggle button at the bottom of the options menu. When I use this, even if I just press the key to quickcast and I do not want it to display a range indicator, it will still very briefly display the range indicator and then fire off the ability. Is there something I am missing or do I just have a slow responsive keyboard? Help please and thank you :)