Sure, but the Mavericks aren't going to win 95% of their games this season. Heck, I'd even bet you that the Mavericks won't win 95% of games remaining on the schedule. But what does winning 19 of 20 have to do with scoring points on a defensive-oriented team on its home floor? That the Mavericks are winning games doesn't lead inexorably to a conclusion that they'll be able to score more on the Spurs than any other team has. It just means that the Mavericks have been winning a lot of games and, I guess, playing well enough to do that.
Of course, in rolling to 19-1, the Mavericks HAVEN'T played against San Antonio and HAVEN'T played in San Antonio, so the 19-1 is entirely independent of the Spurs.
Over a 20 game stretch. But, over the longer course of the NBA season, however, they are only one game better (for the moment) than a Spurs team that has looked to be on cruise control for most of the season.
I guess I just don't follow your logic -- more precisely, I find whatever point you're trying to make wholly illogical.