Dak as a player has been bad against playoff teams also. 'The stats do not lie.
Here's a little snippet from an article after the horrible 2019 season that you can easily find by Googling "Dak vs Playoff Teams"
"Last season, the Cowboys went 8-8 while Prescott threw 30 touchdowns to 11 interceptions. However, 22 of those TDs, and just 3 of those INTs, came against teams that missed the postseason. Prescott led the team to a 7-2 record in such contests. However, when facing teams that made the playoffs, the Cowboys went a miserable 1-6, and Prescott tossed 8 scores and 8 picks."