Umpire strike zone changes to finish games earlier

When watching baseball on television, we get the benefit of seeing whether a pitch entered the strike zone or not. Umpires go by eye, and intentional or not, they tend towards finishing a game over extra innings. Michael Lopez, Brian Mills, and Gus Wezerek for FiveThirtyEight:

The left panel shows the comparative rate of strike calls when, in the bottom of an inning in extras, the batting team is positioned to win — defined as having a runner on base in a tie game — relative to those rates in situations when there’s no runner on base in a tie game. When the home team has a baserunner, umps call more balls, thus setting up more favorable counts for home-team hitters, creating more trouble for the pitcher, and giving the home team more chances to end the game.

I doubt the shift is on purpose, but it’s interesting to see the calls go that way regardless. Also, from a non baseball-viewer, why isn’t there any replay in baseball yet?