That was a strange ending to the Edmonton Anaheim game, but that puck was definitely over the line, so they got the call right even though they botched the process.
The referees of course should NOT have called it a 'good goal on the ice' because certainly no referee actually really saw any indication the puck actually was in. That is a problem. But as for 'how can you 100% for sure tell that puck was completely over the line?' argument, you can see 3/5th of the puck very clearly. It's not rocket science to be able to take that very clear view from above he puck, complete the circle around the puck to know where the rest of the puck covered by Jarry's skate must be, and then draw the goal line across.
Sure you cannot FULLY see the puck, or FULLY see the goal line, but it doesn't take 21st century high tech stuff to be able to say that the puck MUST have been fully across the line based on the images of more than half the puck that you can see.