SOS is actually probably the most underrated part of the NFL. There was not a single team who made the playoffs last year that had a SOS above .500. So its completely relevant.
The SOS you're referring to sounds like the SOS of the games played that year. I don't even think what you're saying is accurate but I could be wrong and I don't feel like looking it up. Regardless, we're talking about comparing last years record to this years SOS which is completely different. edit: changed my mind i did want to look this up. 2006 SOS based on 2005 records: Cincinnati Bengals (.543) New York Giants (.543) New Orleans Saints (.539) Tampa Bay Buccaneers (.539) Pittsburgh Steelers (.531) Kansas City Chiefs (.527) Tennessee Titans (.527) Baltimore Ravens (.523) Houston Texans (.523) Philadelphia Eagles (.520) Oakland Raiders (.516) Washington Redskins (.516) Denver Broncos (.516) Cleveland Browns (.512) St. Louis Rams (.508) Atlanta Falcons (.508) Carolina Panthers (.504) Dallas Cowboys (.504) Arizona Cardinals (.500) San Diego Chargers (.488) Jacksonville Jaguars (.488) Indianapolis Colts (.484) San Francisco 49ers (.477) Buffalo Bills (.477) Detroit Lions (.473) New England Patriots (.473) Miami Dolphins (.469) New York Jets (.465) Minnesota Vikings (.457) Seattle Seahawks (.457) Green Bay Packers (.449) Chicago Bears (.445) 2006 SOS based on 2006 records: Bills 0.566 Titans 0.561 Dolphins 0.538 Raiders 0.538 Patriots 0.533 Buccaneers 0.527 Jaguars 0.526 Bengals 0.525 Giants 0.522 Colts 0.521 Browns 0.521 Lions 0.52 Broncos 0.519 Redskins 0.504 Texans 0.501 Chiefs 0.5 Packers 0.497 49ers 0.493 Cardinals 0.493 Jets 0.487 Vikings 0.487 Steelers 0.484 Saints 0.483 Eagles 0.478 Ravens 0.474 Seahawks 0.473 Chargers 0.466 Panthers 0.463 Rams 0.46 Cowboys 0.459 Falcons 0.448 Bears 0.442
SoS IMO usually matters in retrospect. But it really doesn't tell you who's going to do what just cause how the schedules are set up your previous years position only determines 2 games, everything else is set in stone in regards to who you play....maybe SoS determines where you play them?