There is, unfortunately, a better explanation of how the Braves are doing so well, and that is that they've been extraordinarily lucky so far.
The Braves have scored 93 runs and given up 87 so far. Using Bill James's old Pythagorean Method, at that rate the Braves could expect to win games at about a .533 clip. 19 games is way too few to be statistically significant, but if you multiply 19 by .533, the Braves could reasonably expect to be 10-9 right now. So they're about two games ahead of where they could expect to be, given how many runs they're scoring and giving up.
The Mets, in contrast, have been enormously unlucky thus far. They've scored 109 runs and given up only 57 -- both best in the National League. At that ratio, they can expect to win games at about a .785 pace. They've only played 18 games so far, so they could reasonably expect to have won 14 out of 18. So they're two games behind where they could expect to be. Based on the rates at which the two teams having been scoring and giving up runs so far, the Braves ought to be more like four games back already, not half a game.
A bullpen helps you in close games, and so far the Braves' has been better than the Mets'. But the runs scored/runs allowed numbers are pretty disturbing; the Braves are going to have to do something about that ratio if they want to stay in the race with the Mets.