Here's the thing. Kershaw is currently scheduled to pitch Saturday, which would line him up for Game 1 of NLDS on Thursday. He would not be available to pitch in the tie break game, and would still be available for Game 1. Beuhler is scheduled to go Sunday. He's their likely game 2 starter. So if it comes down to a 1 game playoff, they will likely have to go with Stripling. They'd still be lined up fine for the NLDS.
What I really want to see is the Rockies/Dodgers/Cards all tied at the end of the season. Therefore you get your 1 game playoff for the NL West. The loser plays the Cards to get the 2nd WC spot.