RSA was aware of its weaknesses during the match. They did asses the situation correctly. Much better than India I must say.
They were aware that they cant extract much runs from the pacers. So whatever they do, they will have to do against the spinners. The pacers hold the key which RSA knew but Rohit trusted his spinners way too much.
Once the pacers are back RSA went in to a shell. Not because they choked but because they couldn't maintain it even earlier when they had wickets in hand.
I wouldn't call it choke though. They had a big hole to cover, they knew it, tried to cover it.
Rohit accidentally (and delayed) made the right choice.
It was different from chokes of RSA from before. I don't think klassen would have made a difference if pacers were bowling in the middle overs.