Consider these facts.
A #1 seed gets a bye before playing the weakest seed at home.
A seeding of #2-#4 guarantees a home game in the wildcard round.
The Cowboys are 11-1 at home since the beginning of the 2022 season. They are 6-6 on the road during that same time period.
Not winning the division almost insures three consecutive road games to get to the Super Bowl.
This game may not be a "must win" but if they lose it then the 2nd matchup is absolutely a must win.
If both teams are tied at the end of the season then the first tie breaker is head to head. Assuming that the Cowboys and the Eagles each win a game then the second tie breaker is division record. Currently, they are both undefeated. The third tie breaker is conference record and that's where the Cowboys are at a disadvantage.
A strict definition of "must win" implies losing results in elimination. This does not apply to this game. However, if the Cowboys lose, then the Cowboys would have to achieve a very improbable series of outcomes to some very challenging events. The road that has the highest percentage of success involves defeating the Eagles on Sunday.