That's fair, but here's the thing, I think most of us realized that when the Colts were at 5-2, with the way the Colts had won close, 1-possesion games and lost to teams they had no business losing to (including the Raiders at home), that the Colts probably weren't quite as good as their record indicated.
Conversely, when the Colts were 1-5 last year, and then started to blow out the bad teams on their schedule (something that the '19 team is incapable of), I think we realized that the Colts were probably much better than their record indicated.
Which brings me to my next point. Football Outsiders did a "study" where they analyzed every single regular season game from 1995-2004 to see whether teams that built their records on close wins over good teams did better in the postseason than teams that padded their records with big wins over bad teams.
They did this evaluation based on counting the numbers of "GUTS" and "STOMPS."
STOMP: A win by at least 14 points over a team that will finish the year below .500. GUT: A win by 1-8 points over a team that will finish the year above .500.
The 2003 Patriots are the only team to lead the league in GUT wins and make the Super Bowl.
TL;DR: Winning a bunch of one-possession games, particularly against .500 or sub-.500 teams is oftentimes a strong indicator that a team is not an elite postseason team.
The Colts are winning some of their one-possession games against .500-level teams, but they're also losing a fair share against sub-.500, which is an even bigger red flag.
Full "study" - https://www.footballoutsiders.com/stat-analysis/2005/fo-fox-guts-and-stomps