A wash out would NOT guarantee a semifinal spot for South Africa, as they'll end up with 2 wins and 6 points. In that scenario, it's possible for Pakistan to get to 3 wins and 6 points, thus overtaking South Africa on the points table regardless of the NRR difference. In ICC tournaments (and I think IPL as well), the number of wins are considered before NRR. If both points and wins are tied, then NRR is used to split the teams.
Funny to see a professional journalist who earns his paycheck covering sports wouldn't know a rule that's been in place for a decade now