20 games is a decent sample size to get an idea of what kind of team you have. Sometimes a bad team can go on a great 20-game run, or a great defensive team give up a lot of points over the same stretch.
This team, WITH Shaq, gets great ball movement and easy shots. I seriously believe Rondo and KG are the two best passers at their position, and Pierce may be as well (I know people love LBJ's assist numbers, but Pierce is the smarter, better passer IMO). Shaq is also one of the best passing centers.
They may not keep this pace (highest FG% in quite a number of years), but I don't know why they shouldn't stay atop the league.
Remember, although the starts may all be shooting at a very high clip, we are missing West and JO off the bench, who are significantly more efficient than Wafer and Erden.
This looks like the best offensive team we have had with the Big Three. They may not be the most physical/aggressive, but they are methodical and the smartest. Maybe it's Shaq. Maybe it's Lawrence Frank. Whatever the reason, I don't believe it is simply luck.