On the goal sequence, it's clear that the puck changed trajectory exactly at Slaf's passage, and he immediately celebrated as if he were the scorer.
So, the NHL potentially robbed Slafkovsky of the new record for a 19-year-old in Montreal Canadiens history by taking away his goal, but it's only a matter of time. The Slovak has 24 points in his last 28 games and is on a seven-game points streak. He should surpass Mario Tremblay in the coming days without much trouble.