Most of the guys on the Rogers broadcast missed the boat on the call. Kypper was especially bad when discussing it. They kept looking at it as a goal review type call. Under that scenario, I would say it's a goal. The knock on Andy didn't prevent him from making the save. However, the ref called a penalty for goalie interference, so as soon as the player touched the puck, the play is dead. It would be no difference if the Pitt player has an open cage and behind the play another Pitt player committed a penalty, the play would die as soon as the puck was touched. Doesn't matter how whether or not it would have impacted the goal itself.
The real discussion is should it have been a penalty. My feeling is if a goalie get elbowed in the head in the crease, that's a penalty. If the Pitt player had been pushed in, shouldn't have been a penalty, but he took a dumb angle to the net and smoked the goalie in the head. Player needs to be accountable for that move.