Why is Fizz able to break tethers with his "troll pole" but Vladimir can't?

I think it's fair to compare these abilities because they both grant untargetability. I made a thread about this in the bugs section, and someone told me that tether's can't be broken. If Vladimir goes into his pool while he has something like a Karma tether on him, she'll still get the root/stun/whatever off. But Fizz can simply use his troll pole and dodge it. On a different note, why is the cooldown on Fizz's untarget ability so much shorter than Vladimir's? At max cdr it's like 4.5 seconds. I don't know what the cooldown for Vladimir's pool would be at max cdr, but I'm pretty sure it's more 4.5 seconds, because the cooldown at max rank is 16 seconds, and with 50% cdr that would be 8 seconds (I know you can't get 50% cdr, but I can't do the math in my head, and I know the cooldown is longer than 8 seconds because you can't have 50% cdr).