The Cowboys looked much better on the surface than in depth
As others have noted, Dallas hadn't beaten a single team with a winning record up until they met Seattle. Yes, they led the league in points scored, but who did they run up all those scores against? Look at their record (thanks, pro-football-reference.com). The Cowboys scored 40 or more against the Giants (twice), the Rams, and the Commanders. And yeah, now the Seahawks. Again, we'll get to that. They also hung 30 or more on the Jets, the Panthers, and the Patriots. That last truly makes me happy, but my animus toward the Pats could fill an entire book, let alone one article.
In those seven games, the Cowboys had rolled up 278 of their 347 points through 11 games. That's 39.7 points per game in those wins. Somehow, Dallas managed to mix in an anemic 16 points in a loss to Arizona, another awful team. They did post a 20-17 win over the Chargers, so they did manage to win a difficult game, too.
Without getting too mathy, you can see why I wasn't too impressed with the quality of the 'Boy's wins. The aggregate won-loss record of those seven teams (you know, the crappy teams Dallas beat) is 24-56. That's a .300 winning percentage; not quite as good as the Giants, who I counted twice, as Dallas has played them twice. Add in the three-point win over the 4-7 Chargers, and the winning percentage of their victims skyrockets to .307. Dallas just hadn't beaten anyone, to that point.
And who did the Cowboys lose to, other than the almost-as-atrocious-as-the-Panthers Cardinals? Dallas lost a close game to the Eagles, 28-23, and got obliterated by the 49ers, 42-10. Hey, we feel your pain, Dallas. So in their three losses, the vaunted Cowboys offense managed just 16.3 points per game. Two of those losses just happened to be against the only two teams with a winning record Dallas had faced all season. There are serious benefits to playing in the NFC East.