Vlademir not untargeteble in pool and poppy cced in ult

I have in some games resently seen a vlademir getting healed by a teemo when vlad was in the pool. Both the vlad and i was realy confused over this. And in one of my last games I was a Poppy and ulted a Swain, halfway through the ult i was knocked back and Stunned on a turret by vayne. Nevermove was used earley and i dodged it so i see no reason why i should have been stunned.