We're (so far) kinda seeing the same thing in the AFC:

The two teams who were battling each other til the very end just to win their division (AFC-S, Texans and Titans) outperform the teams who had locked up their divisions or a bye and were essentially coasting the last few weeks: BAL, KC, NE...

Hate them or respect them, Seattle seem to have not let the Niners rest on their laurels and made them play with a "playoff mentality" for the last couple months.