Ezreal's E?

Can someone explain to me how Ezreal can use his E well hes under the effects of blitzcrank's Q or thresh's Q which are cc effects, and when any other marksmen is hit by them they can't use their movement abilities, like graves,lucian,corki who have movement abilities can't seem to use them well being grabbed yet for some reason ezreal is allowed too? why is that?

and i don't mean before or after i mean well they are being grabbed, i see ezreal use his E all the time to cancel out the effects of being grabbed using his E at the exact time he's hit.