Xin Zhao Bug?

I'm sorry if I may seem like some noob that doesn't know the truth about CC or anything- But something that i've noticed playing Malzahar against a Xin Zhao, Is that if He's in AA distance, he can still attack you. Example: He used his Q after two hits I used my Ult right after the 2nd Hit. But his 3rd AA still went through afterwards, Isn't Malzahar's ultimate supposed to suppress not allowing you to attack or do anything?