It was partly a euphemism. I know it's a dumb ass post, and I get that Pillar does not have the best self control at the plate, etc. For a small guy like Pillar he may get a bit more plate coverage with a slightly longer bat though, but I guess there would be a corresponding change in bat speed, timing and feel. I assume the smaller the guy, the smaller the bat. Big strong guys like Chris Davis probably would use a fairly long bat? Pillar just seems to have a higher percentage of hits that come right off the tip of the bat, and dribble to the mound is all. Probably he's just not a great or consistent hitter, as others have pointed out.
Google tells me MLB regulations allow a bat up to 42 inches. Most guys apparently use 33.75-34". Pete Rose used one up to 36"