It's sometime a tendency on a certain pitcher that is picked up on in advanced scouting. If I had to guess, in this situation and based on how that inning went, Steckmesser (who had just come into the game with the bases loaded a couple batters before) was ignoring on the runner when Plattner was throwing the ball back to him (like you alluded to basically, turned his back to him). Either the 3rd base coach gave the runner the green light, or maybe he felt he had it in that situation (he was one of their fastest guys). But if you watch the replay, Plattner checks him, which holds him up. Then the kid breaks and Platter immediately yells at Steckmesser. Ended up an easy out because Plattner was paying attention and doing what he was supposed to do. Sorta made up for his missed tag (although I'm not sure it was actually missed) on the play at home earlier in the game where the throw beat the runner by 10 feet but the Jax St. guy somehow got his hand on the plate under the tag.