In the "After" clip, his feet are way more open in the box. In the first clip, there appears to be almost no body rotation as he "loads" up. He gets very little reach with his arms, almost no hip turn and just a touch of shoulder turn. Moving toward the pitch, it is a total slappy effort, all arms. But it looks like the "After" change has him loading/rotating/extending more as he toe taps and steps toward the plate/pitch (a longer move from the open position). Stop 3 seconds into the 2nd video and it looks like he is in position to almost hurt a pitch. Stop 4 seconds into the "Before" pitch and it is a completely different position. I will admit that the pitch location is different for the two clips, but he is much more loaded in the 2nd clip.
I would have bet a bunch that he had to show more power from that "After" position. If you check out his monthly splits on B-R, you will see that he slugged .455 in Sept, easily his best month of the season. His previous high was .391. Back in '15, he was north of .400 in 4 different months, but had none between April '16 and Sept. '17. '15 was his best slugging season (almost all 2B's and 3B's). Here's his highlight clip from that season. It looks like he played with stance changes then, too. But the more open he is, the more rotation he gets and the more he hurts the ball. https://www.youtube.com/watch?v=UGm_wV_oIpc
Interesting. Nice catch Mal.