I'm a Braves fan. So obviously I didn't like the ruling. But objectively, even if that were the Mets, I wouldn't have liked the way they ruled it. My biggest problem is how far the ball traveled. Being a bit generous, it ended up in shallow left field. It was clearly closer to the outfield than it was the infield. There doesn't seem to be a defined area of the field at which the rule does or doesn't apply. But it seems implicit in the rule and explicit in the title of the rule that the ball has to be hit in or near the infield.
I'd also say it's implicit in the rule that the ball has to be close to the infield because the point of the rule is to protect the runners. In a normal infield fly situation, the fielder could easily fake like he is going to catch it and let it drop at the last second in order to catch the runner off base. The further the ball is hit, the less able the fielder is able to do this since he would have to throw the ball further to get the runner out.
Last night during the play in question, the Braves' runners were off the base and ready to advance because the ball was hit further away from the infield than a normal infield fly situation. And the short stop ended up pulling up because he knew he was running way beyond the infield and was getting to the point where the outfielder was better able to make the catch. So the way the players were behaving made it seem like they knew it wasn't an infield fly situation.
To me there has to be a point at which the rule doesn't apply. Presumably a fly ball could be hit so far and so high that an infielder could use normal effort to catch a ball that ends up on the warning track. I'm not sure how you do that without still having it be a judgment call by the ump. But hopefully this situation gets the league to put more strict definition to the rule.