I was playing blitzcrank support against an ezreal. There is a delay between casting and the teleportation, unlike with flash. If he casts it but does not finish it, it will not be interupted by blitzcranks q, and he will be transported to the desired location, be stunned momentarily, but be otherwise unharmed, other than the damage.
He is not pulled in.
This is working as intended. :)
Trist can do the same thing...... it is just the way the skill are prioritized in the coding.
Not a bug.... unfortunately blinks basically cancel out his pull. So just more to make him the safest poke adc in the game... z.z
Ez was a constant high ban for me because it just dumb amount of CC you can shrug off with arcane shift like Poppy wall slam Morgs snare blitz & Nauts pulls anything that does have a immediate hard CC even then prick still jumps
Honestly, as a 
main this bugged me back in S2 before I improved and learned better.
I now prefer this interaction! Why you ask? Well because Ez thinks he can escape me... MWAHAHAHAHA.
Such a false sense of security makes Ez the best ADC 2 play against as Blitz. For you see, you can just flash or W up to Ez and power fist. What will Ez do to that? Well obviously arcane shift away. WOOPS now its on c/d and you are in pull range...
ggez
You can also do it with Trist if you time it right.
There are a lot of things that can do this. Just more of the hidden stuff you have to play hundreds of games to find/master.
Why are people down voting this thread? The guy had a question about an annoying "mechanic" that is probably was a bug that is now accepted as part of a kit. No need to downvote though. The guy/gal was legitimately curious.
