This stat seems arguably a better measure of the quality of a teams pitchers than its defense.
Disagree, MtH. Basic DIPs theory is that pitchers have very little control over the way a ball in play is fielded. They have control over the balls not in play, like Ks, BBs, HBPs, and HRs. It is not correct at the margins. For example, very high K pitchers seem to induce weaker contact. Flies and groundballs are turned into outs at different rates, so staff full of fly ball pitchers might have a lower BABIP than a normal staff. But, for the most part, when you aggregate a staff of all different kinds of pitchers, the marginal stuff balances out.