Superbowl Outright betting

I can never understand how this market moves in the way it does during a game.

The 49ers rightly shortened after winning last night (I thought they were too big at 6/1) to 3.75.

However while they were entitled to shorten to 5/2after Seattle went ahead late on as they would assume home advantage I don't understand how they do not drift again after Atlanta got bavk up to win.
They now have to travel to the East for the NFC final