The playoff was scheduled to start on #10. They have moved it to 14 so that players don't have to wait so long.
Regarding the slow play penalty, Jackson's group missed the first three checkpoints. The first miss (at #4) is a warning, the second (at #9) a potentlial one-stroke penalty and the third (at #13) a potential two-stroke penalty. If they had missed the final one at #18, they could have been disqualified for missing all four. As it turns out, they had a ruling on the 8th hole which took a few minutes. They missed their checkpoint at #9 by less time than the ruling took so that miss was waived. Given that, they only missed two checkpoints and were penalized one stroke. But, the officials who followed the group after the first miss (we do that with all groups that miss a checkpoint) felt that John Kostis (Peter's son) was making a significant effort to catch up while the others were not so the penalty was waived for him.
Before anyone cries conspiracy, all groups appeal their penalties and about 50% are probably waived. Also, the appeals committee never knows what a player shot so they would not have been sure if Jackson would be medalist or if Kostis would make /miss the playoff. On Monday Nick Taylor, low Am at the US Open, was penalized for slow play also.