Alpha Strike Bug (getting hit by nasus Q while in alpha)

I died to a nasus Q while in Alpha Strike. I alpha striked as soon as the animation for his q started so I should have had plenty of time to be untargetable while in alpha, thus canceling his animation, but it didn't. I have dodged other abilities such as Garen's Q in the past ( https://youtu.be/GC6OqX3JXPY?t=132 as a source for a garen's Q dodge)

P.S. sorry if I sound salty during this video :^( I was just mad