No and yes. No, COSATU doesn't support government accepting loans from the IMF or the World Bank, far from it. If you have other information, please supply it.
But yes, "support for the SA government" is the way a good majority of lefties play politics here. I'm in the same camp as the mainstream of COSATU, which is sometimes called "critical support," namely, promoting those aspects of government policy (particularly in the public health field) where ANC leaders do seek confrontations with corporate power, and also support of the ANC against all the various right-wing opposition parties, all the while hoping that the ANC Left will contest a variety of issues and occasionally win against the ANC Right. Mandela's unequivocally in the latter camp. If you want more evidence I'll send it along.
Support for the IMF is a pretty good place to draw lines in the sand. It's about class consciousness and internationalism, and against a myopic notion that maintaining global financial binds ("balance of payments support") is vital to civilisation against all evidence to the contrary.
And sure, there are ways to develop anti-IMF politics even when you're forced by circumstances to sign off on their loans. When I worked for a while for Jean-Bertrand Aristide in 1995, he managed to do this with quite impressive nuance, largely by building up a Left flank in Haitian civil society and nurturing their critiques of his government's capitulation to neoliberalism. That made it easier for him to say no, when there were opportunities, to the visiting US AID-WB-IFC-IMF teams. With riots in the streets, he was even able to boot out his bourgeois prime minister in October 1995.
What Kim Dae Jung (I'm guessing) and Mandela (I know) do is not anything close; they try to shut down their Left opposition. Perhaps I should upload Mandela's July speech to the SACP or some articles about it, then you'd leave this alone.
In sum, yes, sectarianism is a perennial problem associated with fights within the Left. But Nathan, I'm sorry, you haven't done the work required to prove pro-IMFers and "Progressive Caucus" folk are within what we could minimally define as the Left yet, but I'll keep an open mind.
Yours, P.