The FT disparity is largely the Spurs own doing - or should I say undoing. The Mavs uncharacteristically attacked the basket, thereby getting the Spurs into the penalty early in quarters 1 and 2. Of course, this doesn't apply to Dirk, who was getting his calls by feasting on the tick-tack fouls by Bonner, Mason and a host of others. Many resulted in "and-1" situations.
Meanwhile, the Spurs were busy turning the ball over, dribbling away the shot clock or forcing passes off of pick-n-roll situations into a clogged lane. As far as I'm concerned, the Spurs made that bed for themselves because the shot a higher FG % than the Mavs for most of the entire game.