[Gameplay] Ezreal can blink grabs

Ezreal during a grab, for example, Nautilus'Q.

1. Try to hook Ezreal with Nautilus'Q.
2. Ezreal blinks when anchor hits him.
3. Ezreal gets the damage and the stun but blinks to targeted location. Nautilus is pulled to Ezreal ex-location.

Every time I play Nautilus against Ezreal this happens. Please, correct or give me a good reason why this happens.

Edit; My point is asking why it is like this, not how it happens. A knock-up should cancel cast for the sake of clarity, and there nothing on Ezreal Blink tooltip that says otherwise.