It's not strictly about metacritic scores, but the review embargo means that there will be a point in time where there is a truckload of Spidey-related review/info/impression hitting all at once, and the narrative that is created from that aggregation of reviews definitely have an impact on consumer anticipation for the game.
When suddenly all games media outlets that have a reach of millions of people combined all shout out to their userbase "SPIDER-MAN IS <REDACTED>!", people will notice even if they aren't explicitly following up on Spidey news, and that last mile in terms of positive review drops are about pushing fence-sitters over the wall.
It's also why games that are expected to review extremely well more often than not have an early embargo - because publishers believe that the score will be good/strong enough that the narrative and awareness about the positive reception will be longer than a 24-hour stretch and will only compound further.