Think choke is a bit harsh - a 12 run loss is hardly contriving defeat at the last hurdle
Neither team could get going through the middle overs and while Aus tracked the SA score most of the way through I think they left themselves too much to do at the end .... probably arrogance of assuming that their bowlers did a better job than SA's would be able to at the death etc.
Interesting that while David Warner carried his bat, he chewed up 9 more balls to score 3 less runs total than de Kock ... pretty much your 12 run difference right there between those at the top who had the benefit of the harder ball and opening powerplay.
Amazing fielding by Smith though. He knocked 2 sixes back into play and saved 4. In total I think he turned what could have been 16 runs in boundaries into only 5 saving 11. Some pretty good fielding by Faf as well.