Positioning?  You’d expect to see the effect of positioning show up more in BABIP, but hitters getting stronger might counteract, or at least mask, that effect.

But…if more plays are routine, rather than tough “shoulda made it, but…” plays, that would reduce the error rate.  And it the players are better positioned, that would seem to make some plays more routine.

Also, I’d be interested to see the rates for bunts broken out.  It seems like bunts generate more errors because of the rushed nature of a play on a good bunt, and if the rate of bunt attempts (both sacs and for hits) went down, perhaps overall error rate would too.

And hey, while I’m at it, the error rate on bunts might tell us something about the quality of bunting.  The nostalgic types among us would probably say that in the past, more players could bunt better, and that they would run out sac bunts, etc.  That would make more plays closer.  I have no idea whether the nostalgic view is true or not, though I suspect it is if you go back far enough.