It's not a controversial goal if you actually know the rules for why the goal counted. This is the rule:
“The video review process shall be permitted to assist the Referees in determining the legitimacy of all potential goals (e.g. to ensure they are “good hockey goals”). For example (but not limited to), pucks that enter the net by going through the net meshing, pucks that enter the net from underneath the net frame, pucks that hit the spectator netting prior to being directed immediately into the goal, pucks that enter the net undetected by the Referee, etc. This would also include situations whereby the Referee stops play or is in the process of stopping the play because he has lost sight of the puck and it is subsequently determined by video review that the puck crosses (or has crossed) the goal line and enters the net as the culmination of a continuous play where the result was unaffected by the whistle (i.e., the timing of the whistle was irrelevant to the puck entering the net at the end of a continuous play).”
This goal counted because the puck was on its way into the net when the whistle was blown, so blowing the whistle early didn't impact whether the goal was scored or not. It's the same concept for when a goal counts when the net is knocked off. If a puck is going in the net and the net gets knocked off while the puck is already on its trajectory into the net, it's a good goal.
Why the Sissons goal didn't count? This rule only applies if the puck is already on a trajectory going into the net when the whistle is blown. Sissons scored after the play was blown dead.