MFL is showing 20 points allowed as well. I remember reading that some sites treat the offense as defense immediately after a turnover... that is to say, the Steelers Offense is considered Defense after the turnover, while the ball is still live. I am ALWAYS down for a correction that favors my team, but don't expect it.
There was a Shonn Greene fumble taken away this week, though... who knows. MFL's scoring isn't official until Saturday. I don't play on Yahoo anymore.