There was some discussion on whether or not the play should stand, but there appeared to be more of a focus on whether Leafs captain John Tavares had knocked the puck down with a high stick. Ultimately, it was deemed that Tavares did not touch the puck with a high stick, but then the attention quickly turned to whether or not Matthews had used a "distinct kicking motion".
The review was not very long and the goal was ultimately called back, which is a bit of a surprise, given the fact that it was not egregious and that the call on the ice was a good goal.
While the clip below from TicTacTOmar is not a full speed clip and it does show Matthews inching his toe forward after redirecting the puck, it did not reflect what we saw at full speed, which was a redirection with a very slight forward motion.
If reviews on plays are not definitive, the call on the ice typically stands, however, nobody seems to really know what is and is not a penalty, offside, goalie interference or kicking motion anymore. At this point, it appears to be all at the discretion of the officials. Unfortunately, in this case, it cost Auston Matthews a share of a longstanding NHL record.